Add nova-cells-v1 to experimental queue jobs

The legacy-tempest-dsvm-cells job is being moved into the
nova repo and renamed to nova-cells-v1. This change adds
the new job name to the in-tree definition of the experimental
queue jobs that run on tempest changes. A project-config change
will depend on this patch to undefine the legacy job name from
being used on tempest changes.

Depends-On: https://review.openstack.org/549780
Change-Id: If6b7e59e71739361dcb0d246fca3fcf08af3514d

.zuul.yaml

@@ -209,6 +209,18 @@
     gate:
       jobs:
         - nova-multiattach
+    experimental:
+      jobs:
+        - nova-cells-v1:
+            irrelevant-files:
+              - ^(test-|)requirements.txt$
+              - ^.*\.rst$
+              - ^doc/.*$
+              - ^etc/.*$
+              - ^releasenotes/.*$
+              - ^setup.cfg$
+              - ^tempest/hacking/.*$
+              - ^tempest/tests/.*$
     periodic-stable:
       jobs:
         - tempest-full-queens