Use openstack-tox-cover template

Use openstack-tox-cover template, this runs the cover job
in the check queue only.

Remove jobs and use template instead.

Change-Id: I28111ced5dececccaa38e0033aac920279c45381

.zuul.yaml

@@ -12,8 +12,10 @@
       - openstack/python-monascaclient
       - openstack/tempest
     voting: false
+
 - project:
     templates:
+      - openstack-cover-jobs
       - openstack-python-jobs
       - openstack-python35-jobs
       - openstack-python36-jobs
@@ -23,9 +25,5 @@
     check:
       jobs:
         - monascaevents-tempest-events-base
-        - openstack-tox-cover
     gate:
       queue: monasca
-    post:
-      jobs:
-        - openstack-tox-cover