##### SUMMARY
<!--- Explain the problem briefly below -->
If the `datacenter` key is not defined, `vmware_guest_screenshot` while fail with the following error:

```
TASK [vmware_guest_screenshot : take screenshot of virtual machine's console and download to local] **********************************************
task path: /home/goneri/.ansible/test/tmp/vmware_guest_screenshot-yyx29421-ÅÑŚÌβŁÈ/test/integration/targets/vmware_guest_screenshot/tasks/main.yml:38
<testhost> ESTABLISH LOCAL CONNECTION FOR USER: goneri
<testhost> EXEC /bin/sh -c 'echo ~goneri && sleep 0'
<testhost> EXEC /bin/sh -c '( umask 77 && mkdir -p "` echo /home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069 `" && echo ansible-tmp-1565778524.0166469-178908954277069="` echo /home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069 `" ) && sleep 0'     
Using module file /home/goneri/git_repos/ansible_projects/c/lib/ansible/modules/cloud/vmware/vmware_guest_screenshot.py
<testhost> PUT /home/goneri/.ansible/tmp/ansible-local-3806uqeztqz4/tmplgf85opc TO /home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py                                                                                                    
<testhost> EXEC /bin/sh -c 'chmod u+x /home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/ /home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py && sleep 0'                                                           
<testhost> EXEC /bin/sh -c 'ESXI1_HOSTNAME=root ESXI1_PASSWORD='"'"'!234AaAa56'"'"' ESXI1_USERNAME=esxi1.test ESXI2_HOSTNAME=root ESXI2_PASSWORD='"'"'!234AaAa56'"'"' ESXI2_USERNAME=esxi2.test VCENTER_HOSTNAME=vcenter.test VCENTER_PASSWORD='"'"'!234AaAa56'"'"' VCENTER_USERNAME=administrator@vsphere.local VMWARE_PROXY_HOST='"'"''"'"' VMWARE_PROXY_PORT=0 VMWARE_VALIDATE_CERTS=False /home/goneri/git_repos/ansible_projects/c/.virtualenv/py37/bin/python /home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py && sleep 0'           
<testhost> EXEC /bin/sh -c 'rm -f -r /home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/ > /dev/null 2>&1 && sleep 0'
The full traceback is:
Traceback (most recent call last):
  File "/home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py", line 139, in <module>
    _ansiballz_main()
  File "/home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py", line 131, in _ansiballz_main                                                                                                                                                
    invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)
  File "/home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py", line 65, in invoke_module
    spec.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/tmp/ansible_vmware_guest_screenshot_payload_ka1817jv/__main__.py", line 293, in <module>
  File "/tmp/ansible_vmware_guest_screenshot_payload_ka1817jv/__main__.py", line 285, in main
  File "/tmp/ansible_vmware_guest_screenshot_payload_ka1817jv/__main__.py", line 251, in take_vm_screenshot
  File "/tmp/ansible_vmware_guest_screenshot_payload_ka1817jv/__main__.py", line 169, in generate_http_access_url
AttributeError: 'PyVmomiHelper' object has no attribute 'get_parent_datacenter'

fatal: [testhost]: FAILED! => {
    "changed": false,
    "module_stderr": "Traceback (most recent call last):\n  File \"/home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py\", line 139, in <module>\n    _ansiballz_main()\n  File \"/home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py\", line 131, in _ansiballz_main\n    invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)\n  File \"/home/goneri/.ansible/tmp/ansible-tmp-1565778524.0166469-178908954277069/AnsiballZ_vmware_guest_screenshot.py\", line 65, in invoke_module\n    spec.loader.exec_module(module)\n  File \"<frozen importlib._bootstrap_external>\", line 728, in exec_module\n  File \"<frozen importlib._bootstrap>\", line 219, in _call_with_frames_removed\n  File \"/tmp/ansible_vmware_guest_screenshot_payload_ka1817jv/__main__.py\", line 293, in <module>\n  File \"/tmp/ansible_vmware_guest_screenshot_payload_ka1817jv/__main__.py\", line 285, in main\n  File \"/tmp/ansible_vmware_guest_screenshot_payload_ka1817jv/__main__.py\", line 251, in take_vm_screenshot\n  File \"/tmp/ansible_vmware_guest_screenshot_payload_ka1817jv/__main__.py\", line 169, in generate_http_access_url\nAttributeError: 'PyVmomiHelper' object has no attribute 'get_parent_datacenter'\n",                      
    "module_stdout": "",
    "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error",
    "rc": 1
}
```

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
vmware_guest_screenshot

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
devel branch
```

##### STEPS TO REPRODUCE

https://github.com/ansible/ansible/blob/d8d00c36fa41ddc384966249005f7a922ead43c1/test/integration/targets/vmware_guest_screenshot/tasks/main.yml#L14-L20

##### ACTUAL RESULTS

The backtrace above.
on ESXi host. If C(local_path) is set to a valid path on local machine, then the screenshot file will be
       downloaded from ESXi host to the local directory.'
     - 'If not download screenshot file to local machine, you can open it through the returned file URL in screenshot
       facts manually.'
     type: str
extends_documentation_fragment: vmware.documentation
'''
EXAMPLES = '''
- name: take a screenshot of the virtual machine console
  vmware_guest_screenshot:
    validate_certs: no
    hostname: "{{ vcenter_hostname }}"
    username: "{{ vcenter_username }}"
    password: "{{ vcenter_password }}"
    datacenter: "{{ datacenter_name }}"
    folder: "{{ folder_name }}"
    name: "{{ vm_name }}"
    local_path: "/tmp/"
  delegate_to: localhost
  register: take_screenshot
- name: Take a screenshot of the virtual machine console using MoID
  vmware_guest_screenshot:
    validate_certs: no
    hostname: "{{ vcenter_hostname }}"
    username: "{{ vcenter_username }}"
    password: "{{ vcenter_password }}"
    datacenter: "{{ datacenter_name }}"
    folder: "{{ folder_name }}"
    moid: vm-42
    local_path: "/tmp/"