Fixed login error message box in LoginScreen page
Fix added for showing error message returned from server to client
browser. User is now notified with proper error messages returned by
server.
https://bugzilla.redhat.com/show_bug.cgi?id=1293870
Signed-off-by: Abhijeet Kasurde <akasurde@redhat.com>
Reviewed-By: Petr Vobornik <pvoborni@redhat.com>