Plugin tries using server `clouds.yaml`

[outcatcher]

During development of #41, the following problem found:

            Error:          Not equal: 
                            expected: 204
                            actual  : 500
            Test:           TestPlugin/TestRootRotate
            Messages:       {
                              "errors": [
                                "1 error occurred:\n\t* cloud tf does not exist in clouds.yaml\n\n"
                              ]
                            }

Plugin should ignore OS_ env variables and client configurations existing on the server.