Make pushing zuul refs upstream optional.

And the default -- so that Zuul doesn't need any special gerrit
privileges to run out of the box.

Change-Id: I36411b299c8363d509498ece8ea21f88665ca39a
Reviewed-on: https://review.openstack.org/11589
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins
3 files changed