Default client keytab name

[Sam Hartman]

OK, I'm clearly in the minority here.  I'd like the uid-based tag to
exist.  I'll discuss within Debian whether we'll need to override for
what we do.  We have gssd too, but we also have a bunch of services for
which finding out the appropriate uid is difficult from a configuration
management system because it is machine dependent.
We can hash out how to balance that.