Rename zuul manifest to zuul_prod.

Because puppet scoping is ridiculous.

Change-Id: I5a62a272353a88fe996e946ef3611a8320ba9c30
Reviewed-on: https://review.openstack.org/29011
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins