Drop devstack-gate roles from devstack zuul jobs

Devstack-gate has been retired and relying on a retired repo for roles
in zuul produces errors (because the roles are no longer in the HEAD of
the repo). It doesn't look like devstack actually relies on these roles
in d-g (if it does they can be ported into devstack instead) so we just
drop the roles specifier for d-g in the devstack job.

NOTE(elod.illes): nova-ceph-multistore job is broken in this branch, so
it is set as non-voting in check queue and removed from gate queue
until it gets fixed.

NOTE(elod.illes): grenade is also failing on this branch with cinder
related issue, so it is set as non-voting to be able to merge this
patch to unblock other repos gates.

Conflicts:
  .zuul.yaml

Change-Id: I28a39b31f71153a602d41cefe621a216d09a290f
(cherry picked from commit d487302e60)
(cherry picked from commit 503116557a)
(cherry picked from commit 37f0673893)
(cherry picked from commit 1592b95d70)

.zuul.yaml

@@ -255,7 +255,6 @@
     required-projects:
       - opendev.org/openstack/devstack
     roles:
-      - zuul: opendev.org/openstack/devstack-gate
       - zuul: opendev.org/openstack/openstack-zuul-jobs
     vars:
       devstack_localrc:
@@ -683,6 +682,7 @@
         - nova-live-migration:
             voting: false
         - nova-ceph-multistore:
+            voting: false
             irrelevant-files:
               - ^.*\.rst$
               - ^doc/.*$
@@ -713,10 +713,13 @@
             irrelevant-files:
               - ^.*\.rst$
               - ^doc/.*$
-        - nova-ceph-multistore:
-            irrelevant-files:
-              - ^.*\.rst$
-              - ^doc/.*$
+        # TODO(elod.illes): nova-ceph-multistore is broken in this branch,
+        # so it is set as non-voting in check queue and commented out here
+        # in gate queue until the job gets fixed.
+        # - nova-ceph-multistore:
+        #   irrelevant-files:
+        #     - ^.*\.rst$
+        #     - ^doc/.*$
     # Please add a note on each job and conditions for the job not
     # being experimental any more, so we can keep this list somewhat
     # pruned.