mod_auth_gssapi: enable unique credential caches names
mod_auth_gssapi > 1.4.0 implements support for unique ccaches names.
Without it ccache name is derived from pricipal name.
It solves a race condition in two concurrent request of the same
principal. Where first request deletes the ccache and the second
tries to use it which then fails. It may lead e.g. to a failure of
two concurrent ipa-client-install.
With this feature there are two ccaches so there is no clash.
https://fedorahosted.org/freeipa/ticket/5653
Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
Reviewed-By: Robbie Harwood <rharwood@redhat.com>