Gssd blindly caches machine credentials

We have a problem with rpc.gssd which blindly caches machine credentials.
E.g., if someone deletes /tmp/krb5cc_machine_REALM, rpc.gss does not create
new one until the old one expires. Also, it has problems with clock skew, if
time goes back and gssd thinks that machine credentials are not expired yet.

The following patch tries to use cache but in case of failure, it tries it
again without cache. Any comments?

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