Set refstack-client-*-tempestconf voting again

As the issue with refstack-client-devstack-tempestconf
job was fixed here:
https://review.openstack.org/#/c/628446/
we can set the job as voting again.

Depends-On: https://review.openstack.org/#/c/628446/
Change-Id: I00b803cc818a207255d7d3290b319001bb12738b

.zuul.yaml

@@ -15,8 +15,7 @@
         - python-tempestconf-tempest-packstack-admin
         - python-tempestconf-tempest-packstack-demo
         - tripleo-ci-centos-7-scenario002-standalone
-        - refstack-client-devstack-tempestconf:
-            voting: false
+        - refstack-client-devstack-tempestconf
     gate:
       jobs:
         - python-tempestconf-tempest-devstack-admin
@@ -26,8 +25,7 @@
         - python-tempestconf-tempest-packstack-admin
         - python-tempestconf-tempest-packstack-demo
         - tripleo-ci-centos-7-scenario002-standalone
-        - refstack-client-devstack-tempestconf:
-            voting: false
+        - refstack-client-devstack-tempestconf
 
 - job:
     name: python-tempestconf-devstack-base