##### 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 vm_power not in cacheable_results:
                        cacheable_results[vm_power] = {'hosts': []}
                        self.inventory.add_group(vm_power)
                    cacheable_results[vm_power]['hosts'].append(current_host)
                    self.inventory.add_child(vm_power, current_host)
                    
                    vm_guest_id = vm_obj.obj.config.guestId
                    if vm_guest_id and vm_guest_id not in cacheable_results:
                        cacheable_results[vm_guest_id] = {'hosts': []}
                        self.inventory.add_group(vm_guest_id)
                    cacheable_results[vm_guest_id]['hosts'].append(current_host)
                    self.inventory.add_child(vm_guest_id, current_host)
        for host in hostvars:
            h = self.inventory.get_host(host)
            cacheable_results['_meta']['hostvars'][h.name] = h.vars
        return cacheable_results
    def _populate_host_properties(self, vm_obj, current_host):
        
        vm_properties = self.get_option('properties') or []
        field_mgr = self.pyv.content.customFieldsManager.field
        for vm_prop in vm_properties:
            if vm_prop == 'customValue':
                for cust_value in vm_obj.obj.customValue:
                    self.inventory.set_variable(current_host,
                                                [y.name for y in field_mgr if y.key == cust_value.key][0],
                                                cust_value.value)
            else:
                vm_value = self.pyv._get_object_prop(vm_obj.obj, vm_prop.split("."))
                self.inventory.set_variable(current_host, vm_prop, vm_value)