Update to multi-mirror jeepyb.

Requires https://review.openstack.org/#/c/23771/

Change-Id: If2db2516789a01fc60e6dbd0be062a8bf00ed9bc
Reviewed-on: https://review.openstack.org/23774
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins