##### SUMMARY
Environment variables in plugin do not match Tower credential injector

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
lib/ansible/plugins/inventory/vmware_vm_inventory.py

##### ANSIBLE VERSION
```
ansible 2.8.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /bin/ansible
  python version = 2.7.5 (default, May 20 2019, 12:21:26) [GCC 4.8.5 20150623 (Red Hat 4.8.5-36)]
```
##### CONFIGURATION
```paste below

```

##### OS / ENVIRONMENT
Red Hat Enterprise Linux Server release 7.5

##### STEPS TO REPRODUCE
use vmware inventory plugin with vCenter credential in Ansible Tower
```yaml
---
plugin: vmware_vm_inventory
validate_certs: False
```


##### EXPECTED RESULTS
inventory should be parsed

##### ACTUAL RESULTS
```paste below
 [WARNING]:  * Failed to parse
/var/lib/awx/projects/_16__ansible_inventory/tests/vmware_vm_inventory.yaml
with auto plugin: No setting was provided for required configuration
plugin_type: inventory plugin: vmware_vm_inventory setting: username
```

description: Name of vCenter or ESXi server.
            required: True
            env:
              - name: VMWARE_SERVER
        username:
            description: Name of vSphere admin user.
            required: True
            env:
              - name: VMWARE_USERNAME
        password:
            description: Password of vSphere admin user.
            required: True
            env:
              - name: VMWARE_PASSWORD
        port:
            description: Port number used to connect to vCenter or ESXi Server.
            default: 443
            env:
              - name: VMWARE_PORT
        validate_certs:
            description:
            - Allows connection when SSL certificates are not valid. Set to C(false) when certificates are not trusted.
            default: True
            type: boolean
        with_tags:
            description:
            - Include tags and associated virtual machines.
            - Requires 'vSphere Automation SDK' library to be installed on the given controller machine.
            - Please refer following URLs for installation steps
            - 'https://code.vmware.com/web/sdk/65/vsphere-automation-python'