ipatests: Make sure we re-kinit as admin before adding the disabledipauser
When we add the disabledipauser during the setup class part of the
BaseTestLegacyClient, we need to make sure that we re-kinit admin
since we do ntpsync with the AD just before that, which can render
the previous ticket invalid.
Reviewed-By: Nathaniel McCallum <npmccallum@redhat.com>