Only specify to USE_KEYRING as the api_key/password when we actually got a…

Only specify to USE_KEYRING as the api_key/password when we actually got a keyring_username from ~/.pyrax.cfg

lib/ansible/module_utils/rax.py

@@ -45,6 +45,7 @@ def setup_rax_module(module, rax_module):
         username = username or os.environ.get('RAX_USERNAME')
         if not username:
             username = rax_module.get_setting('keyring_username')
+            if username:
                 api_key = 'USE_KEYRING'
         if not api_key:
             api_key = os.environ.get('RAX_API_KEY')