Add grizzly bitrot jobs.

Change-Id: I3a2a3aee17ed8a10be8b2cdbf1dce372e063c781
Reviewed-on: https://review.openstack.org/26682
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins