webadmin: Wrong error message is shown, when SuperUser permissions are removing from admin internal

The following bug contains two errors:
1. Fixing error message: Cannot ${action} ${type}.
2. In canDoAction() , if we failed at first condition, no reason to perfrom additional checks

Change-Id: I825a379b383fd923046e17e6f1d27c6003c48900
Bug-Url: https://bugzilla.redhat.com/924880
Signed-off-by: Michael Kublin <mkublin@redhat.com>