Use templates for cover and lower-constraints

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

Use openstack-lower-constraints-jobs template.

Remove jobs that are part of the templates.

Change-Id: I119010c3e085d941a2c4e0cca53e71e029833667

.zuul.yaml

@@ -1,32 +1,23 @@
 - project:
     templates:
       - check-requirements
-      - release-notes-jobs-python3
+      - nodejs4-jobs
+      - openstack-cover-jobs-horizon
+      - openstack-lower-constraints-jobs
       - openstack-python-jobs-horizon
       - openstack-python35-jobs-horizon
-      - nodejs4-jobs
+      - release-notes-jobs-python3
     check:
       jobs:
         - murano-dashboard-sanity-check
-        - openstack-tox-lower-constraints
         - horizon-openstack-tox-python3-django111
-        - openstack-tox-cover:
-            voting: false
-            required-projects:
-              - openstack/horizon
     gate:
       jobs:
-        - openstack-tox-lower-constraints
         - horizon-openstack-tox-python3-django111
-
-    post:
-      jobs:
-        - openstack-tox-cover:
-            required-projects:
-              - openstack/horizon
     experimental:
       jobs:
         - legacy-dashboard-dsvm-selenium-package
+
 - job:
     name: murano-dashboard-sanity-check
     parent: legacy-dsvm-base