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.

Sort list of templates alphabetically.

Change-Id: I4175d4b66a488f2b332f5e540dd433837f9ad440

.zuul.yaml

@@ -25,24 +25,19 @@
 
 - project:
     templates:
+      - check-requirements
+      - lib-forward-testing
+      - lib-forward-testing-python3
+      - openstack-cover-jobs
+      - openstack-lower-constraints-jobs
       - openstack-python-jobs
       - openstack-python35-jobs
       - openstack-python36-jobs
       - publish-openstack-docs-pti
-      - check-requirements
-      - lib-forward-testing
-      - lib-forward-testing-python3
       - release-notes-jobs-python3
     check:
       jobs:
         - cinderclient-dsvm-functional
         - cinderclient-dsvm-functional-identity-v3-only
-        - openstack-tox-lower-constraints
         - openstack-tox-pylint:
             voting: false
-    gate:
-      jobs:
-        - openstack-tox-lower-constraints
-    post:
-      jobs:
-        - openstack-tox-cover