ceilometer: enable gate-grenade-dsvm-forward

Enable Grenade gating for openstack/ceilometer project.

Implements: blueprint grenade-upgrade-testing
Change-Id: I23495fd8c13ad7c2c831f6ba4b76d035182f869c
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge "ceilometer: enable gate-grenade-dsvm-forward"