Make the nova-next job voting and gating

Bug 1747511 was fixed with change
I363182e916480c734cc37f279e8e89c8f3ec653c in Queens
so we can make the nova-next job voting now.

We want this job voting and gating since it tests
some things not found in other job configurations,
like TLS proxy, service user tokens, and post-test hooks
for nova-manage commands like archive_deleted_rows.

Change-Id: I4cfc3b100f8829deb97e491f40a3020b3c8eb026
Related-Bug: #1747511

.zuul.yaml

@@ -97,8 +97,6 @@
       post-test scripts to ensure those scripts are still working,
       e.g. archive_deleted_rows. In Queens, this job started testing the
       TLS console proxy code in the libvirt driver.
-    # TODO(mriedem): Make this voting once bug 1747511 is fixed.
-    voting: false
     run: playbooks/legacy/nova-next/run.yaml
     post-run: playbooks/legacy/nova-next/post.yaml
 
@@ -113,6 +111,7 @@
     gate:
       jobs:
         - nova-multiattach
+        - nova-next
         - nova-tox-functional
         - nova-tox-functional-py35
     experimental: