ui_tests: stabilization fixes
    
    This patch aims to fix the following tests which seems to be quite
    unstable recently:
    
    test_user::test_actions - closing notification and moving to element
    to have screenshot of current place.
    
    test_user::certificates - add wait() / close_notification
    
    Also adds missing @screenshot decorator to test_user_misc method.
    
    Reviewed-By: Pavel Picka <ppicka@redhat.com>