Add warnings for Authentication Server commands

Add warnings for Authentication Server commands

For each command only useful with the Authentication Server, add
warnings that the Authentication Server is obsolete and will be
removed in a future version of OpenAFS.  Encourage people who care
to update uss to work with a modern Kerberos KDC, recommend kinit
and aklog or klog.krb5 over klog, and warn that klog will be of
limited use without an Authentication Server.

Change-Id: Idc78ba548134b83ac1eea0fb81a5bc38a431bb38
Reviewed-on: http://gerrit.openafs.org/2052
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>