pull grenade-dsvm-neutron from gate queue because it's non voting

grenade-dsvm-neutron is not going to pass for a while because it's
found a substantial issue with the neutron migration models when
it comes to turning on services in an extant environment. We should
pull it off the gate queue (leave it in check only) to save nodes
a noise in elastic-recheck gate failures.

Change-Id: Ie7ccff10dd515e26fa6865114cb6ccc55177d5c5
Merge "pull grenade-dsvm-neutron from gate queue because it's non voting"