Add apache license header to zuul module manifest.

Change-Id: I8374f389dc0a470a9e12b2987b3bd45dd07a9b74
Reviewed-on: https://review.openstack.org/27513
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Khai Do <zaro0508@gmail.com>
Reviewed-by: Paul Belanger <paul.belanger@polybeacon.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Antoine Musso <hashar@free.fr>
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Approved: Monty Taylor <mordred@inaugust.com>
Tested-by: Jenkins