fixes premature sys.exit in ipa-replica-manage del
    
    Deletion of a replica would fail should there
    be no RUVs on the server.
    
    Also removed some dead code in del_master_managed which might
    cause premature exit if RuntimeError occurs.
    
    https://fedorahosted.org/freeipa/ticket/5307
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>