Split gate-noop and gate-grenade gate queues.

* .../zuul/layout.yaml: Grenade was running
gate-noop and the grenade tests which put all projects using the
gate-noop jobs in the gate queue with the core OpenStack projects.
Add a gate-grenade-noop and use that with Grenade to split the two
pipelines.

* .../jenkins_job_builder/config/misc.yaml: Add gate-grenade-noop.

Change-Id: I3cdc164b33c569ad70ec1105f915e25a2369ae8b
Merge "Split gate-noop and gate-grenade gate queues."