Make the nova-multiattach job non-voting temporarily

Since Icb971831c8d4fe5f940d9e7993d53f1c3765e30f merged
in devstack to use the Queens UCA, the nova-multiattach
job has been failing to start nova-compute due to permission
errors connecting to libvirt, which probably has something
to do with the stack user not having access to the proper
libvirt(d) group.

It's weird since this was working in change
I0962474ff6dfc5fa97670c09a1af97a0f34cd54f to make the
nova-multiattach job use the Queens UCA.

Anyway, let's make it non-voting to stop the bleeding while
we can figure out the actual problem.

Change-Id: I3911c902cecfa8e66fccffd9fe0e4f462eacd588
Related-Bug: #1763382

.zuul.yaml

@@ -99,6 +99,8 @@
     branches: ^(?!stable/(newton|ocata|pike)).*$
     run: playbooks/legacy/nova-multiattach/run.yaml
     post-run: playbooks/legacy/nova-multiattach/post.yaml
+    # TODO(mriedem): Make this job voting and gating once bug 1763382 is fixed.
+    voting: false
 
 - job:
     name: nova-next
@@ -126,7 +128,6 @@
     gate:
       jobs:
         - nova-cells-v1
-        - nova-multiattach
         - nova-next
         - nova-tox-functional
         - nova-tox-functional-py35