Reconfigure jobs for gearman plugin.

And reconfigure zuul.openstack.org for gearman.

Change-Id: I251135e3b0f2638bcc0d817dadb549c0fc2e0d2f
Reviewed-on: https://review.openstack.org/32164
Tested-by: Jenkins
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: James E. Blair <corvus@inaugust.com>