slapi-nis: update configuration to allow external members of IPA groups
    
    Currently in an environment with trust to AD the compat tree does not
    show AD users as members of IPA groups. The reason is that IPA groups
    are read directly from the IPA DS tree and external groups are not
    handled.
    
    slapi-nis project has added support for it in 0.55, make sure we update
    configuration for the group map if it exists and depend on 0.55 version.
    
    https://fedorahosted.org/freeipa/ticket/4403
    
    Reviewed-By: Tomas Babej <tbabej@redhat.com>