Make lint work on Fedora 22.
    
    pylint added 'confidence' parameter to 'add_message' method of PyLinter.
    To be compatible with both, pre- and post- 1.4  IPALinter must accept
    the parameter but not pass it over.
    Also python3 checker was added and enabled by default. FreeIPA is still
    not ready for python3.
    Additionally few false-positives was marked.
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>