##### 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
```

"""
        super(InventoryModule, self).parse(inventory, loader, path, cache=cache)
        cache_key = self.get_cache_key(path)
        config_data = self._read_config_data(path)
        
        self._consume_options(config_data)
        self.pyv = BaseVMwareInventory(
            hostname=self.get_option('hostname'),
            username=self.get_option('username'),
            password=self.get_option('password'),
            port=self.get_option('port'),
            with_tags=self.get_option('with_tags'),
            validate_certs=self.get_option('validate_certs')
        )
        self.pyv.do_login()
        self.pyv.check_requirements()
        source_data = None
        if cache:
            cache = self.get_option('cache')
        update_cache = False
        if cache:
            try:
                source_data = self._cache[cache_key]
            except KeyError:
                update_cache = True
        using_current_cache = cache and not update_cache
        cacheable_results = self._populate_from_source(source_data, using_current_cache)
        if update_cache:
            self._cache[cache_key] = cacheable_results
    def _populate_from_cache(self, source_data):