##### 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
```

if self.validate_certs and not hasattr(ssl, 'SSLContext'):
            raise AnsibleError('pyVim does not support changing verification mode with python < 2.7.9. Either update '
                               'python or set validate_certs to false in configuration YAML file.')
        ssl_context = None
        if not self.validate_certs and hasattr(ssl, 'SSLContext'):
            ssl_context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
            ssl_context.verify_mode = ssl.CERT_NONE
        service_instance = None
        try:
            service_instance = connect.SmartConnect(host=self.hostname, user=self.username,
                                                    pwd=self.password, sslContext=ssl_context,
                                                    port=self.port)
        except vim.fault.InvalidLogin as e:
            raise AnsibleParserError("Unable to log on to vCenter or ESXi API at %s:%s as %s: %s" % (self.hostname, self.port, self.username, e.msg))
        except vim.fault.NoPermission as e:
            raise AnsibleParserError("User %s does not have required permission"
                                     " to log on to vCenter or ESXi API at %s:%s : %s" % (self.username, self.hostname, self.port, e.msg))
        except (requests.ConnectionError, ssl.SSLError) as e:
            raise AnsibleParserError("Unable to connect to vCenter or ESXi API at %s on TCP/%s: %s" % (self.hostname, self.port, e))
        except vmodl.fault.InvalidRequest as e:
            
            raise AnsibleParserError("Failed to get a response from server %s:%s as "
                                     "request is malformed: %s" % (self.hostname, self.port, e.msg))
        except Exception as e:
            raise AnsibleParserError("Unknown error while connecting to vCenter or ESXi API at %s:%s : %s" % (self.hostname, self.port, e))
        if service_instance is None:
            raise AnsibleParserError("Unknown error while connecting to vCenter or ESXi API at %s:%s" % (self.hostname, self.port))
        atexit.register(connect.Disconnect, service_instance)
        return service_instance.RetrieveContent()
    def check_requirements(self):