##### SUMMARY
get_vm() method vmware.py module utility fails with KeyError if uuid is not in the module param from whch method is invoked

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
vmware.py module util

##### ANSIBLE VERSION
```
ansible 2.9.0.dev0
```

##### OS / ENVIRONMENT
Ubuntu 16

##### STEPS TO REPRODUCE
Creating new module. 'uuid' is not in my module arguments. 
Called get_vm() 

pyv = PyVmomi(module=module)
vm = pyv.get_vm()

##### EXPECTED RESULTS
Call should return vm_id if it exists

##### ACTUAL RESULTS
```
Get error
An exception occurred during task execution. To see the full traceback, use -vvv. The error was: KeyError: 'uuid'
fatal: [localhost]: FAILED! => {"changed": false, "module_stderr": "Traceback (most recent call last):\n  File
\"/home/vmware/.ansible/tmp/ansible-tmp-1565095783.75439-259726275713856/AnsiballZ_vmware_content_deploy_template.py\", line 125, in <module>\n    _ansiballz_main()\n  File \"/home/vmware/.ansible/tmp/ansible-tmp-1565095783.75439-259726275713856/AnsiballZ_vmware_content_deploy_template.py\", line 117, in _ansiballz_main\n    invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)\n  File \"/home/vmware/.ansible/tmp/ansible-tmp-1565095783.75439-259726275713856/AnsiballZ_vmware_content_deploy_template.py\", line 51, in invoke_module\n    spec.loader.exec_module(module)\n  File \"<frozen importlib._bootstrap_external>\", line 665, in exec_module\n  File \"<frozen importlib._bootstrap>\", line 222, in _call_with_frames_removed\n  File \"/tmp/ansible_vmware_content_deploy_template_payload_69cftg21/__main__.py\", line 271, in <module>\n  File \"/tmp/ansible_vmware_content_deploy_template_payload_69cftg21/__main__.py\", line 241, in main\n  File \"/tmp/ansible_vmware_content_deploy_template_payload_69cftg21/ansible_vmware_content_deploy_template_payload.zip/ansible/module_utils/vmware.py\", line 891,
in get_vm\nKeyError: 'uuid'\n", "module_stdout": "", "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error", "rc": 1}

```

result = dict()
    interval = 15
    while timeout > 0:
        if vm.runtime.powerState.lower() == 'poweredoff':
            break
        time.sleep(interval)
        timeout -= interval
    else:
        result['failed'] = True
        result['msg'] = 'Timeout while waiting for VM power off.'
    return result
class PyVmomi(object):
    def __init__(self, module):
        """
        Constructor
        """
        if not HAS_REQUESTS:
            module.fail_json(msg=missing_required_lib('requests'),
                             exception=REQUESTS_IMP_ERR)
        if not HAS_PYVMOMI:
            module.fail_json(msg=missing_required_lib('PyVmomi'),
                             exception=PYVMOMI_IMP_ERR)
        self.module = module
        self.params = module.params
        self.current_vm_obj = None
        self.si, self.content = connect_to_api(self.module, return_si=True)
        self.custom_field_mgr = []
        if self.content.customFieldsManager:  
            self.custom_field_mgr = self.content.customFieldsManager.field
    def is_vcenter(self):