Make Zuul's Jenkins comments snarky.

Make Zuul's Jenkins comments snarky for April Fools' Day.

Change-Id: Ifeed4122bfe814dac1881086eb1c9c68db8cd1eb
Reviewed-on: https://review.openstack.org/25797
Reviewed-by: Davanum Srinivas (dims) <davanum@gmail.com>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Khai Do <zaro0508@gmail.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins