Hammer CLI

Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1465552

Description of problem:

Unsuccessful `hammer auth login` takes down existing session.

Steps to Reproduce:
1. authenticate e.g. as admin

~]# hammer auth status
Session exist, currently logged in as 'admin'

2. run `hammer auth login` with invalid credentials

~]# hammer auth login
[Foreman] Username: jjj
[Foreman] Password for jjj: 
Invalid username or password

3. the admin session is terminated

~]# hammer auth status
You are currently not logged in

Expected results:

Session perisists, cli notifies user that the credentials were invalid and the user is still logged in as 'admin'.