Server Roles: make server-{show,find} utilize role information
    
    server-show command will now display list of roles enabled on the master
    (unless `--raw` is given).
    
    server-find gained `--servroles` options which facilitate search for server
    having one or more enabled roles.
    
    http://www.freeipa.org/page/V4/Server_Roles
    https://fedorahosted.org/freeipa/ticket/5181
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Pavel Vomacka <pvomacka@redhat.com>