s4-selftest: Avoid running kinit for each new connection

s4-selftest: Avoid running kinit for each new connection

Kerberos is efficient when the credentials cache is set up once and
then reused.

Sadly this test creates a user, does a test and deletes the user, over
and over.

For this, using NTLM saves a little time, but we also stress the rest
of the DB, and should rework the test.

Andrew Bartlett

Autobuild-User: Andrew Bartlett <abartlet@samba.org>
Autobuild-Date: Mon Feb 20 00:49:56 CET 2012 on sn-devel-104