tsiggss: regenerate kerberos credentials

tsiggss: regenerate kerberos credentials

The existing set of kerberos credential used deprecated algorithms
which are not supported by some implementations in FIPS mode.
Regenerate the saved credentials using more modern algorithms.

Added tsiggss/krb/setup.sh which sets up a test KDC with the required
principals for the system test to work.  The tsiggss system test
needs to be run once with this active and KRB5_CONFIG appropriately.
set.  See tsiggss/tests.sh for an example of how to do this.