The rpc.gssd scans for any suitable kerberos ticket. In cross-realm

The rpc.gssd scans for any suitable kerberos ticket. In cross-realm
environment this may not be the desired behaviour. Therefore a new
option, -R preferred realm, is presented so that the rpc.gssd prefers tickets
from this realm. By default, the default realm is preferred.

Signed-off-by: Lukas Hejtmanek <xhejtman@ics.muni.cz>
Signed-off-by: Kevin Coffman <kwc@citi.umich.edu>
Signed-off-by: Steve Dickson <steved@redhat.com>