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.

Move template list to top of project stanza to follow common practice
and sort list of templates.

Change-Id: Iaa754888d1c6fbe6a563098507c1eb71300ab845

.zuul.yaml

@@ -1,25 +1,21 @@
 - 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
+      - periodic-stable-jobs
+      - publish-openstack-docs-pti
+      - release-notes-jobs-python3
     check:
       jobs:
         - openstack-tox-functional
         - openstack-tox-functional-py35
-        - openstack-tox-lower-constraints
-        - openstack-tox-cover
     gate:
       jobs:
         - openstack-tox-functional
         - openstack-tox-functional-py35
-        - openstack-tox-lower-constraints
-    templates:
-      - openstack-python-jobs
-      - openstack-python35-jobs
-      - check-requirements
-      - publish-openstack-docs-pti
-      - release-notes-jobs-python3
-      - lib-forward-testing
-      - lib-forward-testing-python3
-      - periodic-stable-jobs
-      - openstack-python36-jobs
-    post:
-      jobs:
-        - openstack-tox-cover