Ticket 48050 - Refactor acctpolicy_plugin suite
    
    Description: Add 3 test cases, fix docstrings and add pytest.raises.
    
    https://fedorahosted.org/389/ticket/48050
    
    Reviewed by: spichugi
    
    Signed-off-by: Simon Pichugin <spichugi@redhat.com>