Cleanup .zuul.yaml

* Sort list of templates alphabetically
* Use lower-constraints-jobs template, remove jobs
* Use tox-cover template that runs job voting in gate instead of
  in post queue, remove job

Change-Id: Ifdfa5c4b27cdeb1b4671188bf9fc30cb7f721c07

.zuul.yaml

@@ -123,24 +123,24 @@
 
 - project:
     templates:
-      - openstack-python-jobs
-      - openstack-python35-jobs
-      - openstack-python36-jobs
-      - release-notes-jobs-python3
-      - publish-openstack-docs-pti
       - 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
+      - release-notes-jobs-python3
     check:
       jobs:
         - glanceclient-dsvm-functional-v1
         - glanceclient-dsvm-functional
-        - openstack-tox-lower-constraints
     gate:
       jobs:
         - glanceclient-dsvm-functional-v1
         - glanceclient-dsvm-functional
-        - openstack-tox-lower-constraints
     periodic:
       jobs:
         - glanceclient-tox-py27-keystone-tips
@@ -150,6 +150,3 @@
     experimental:
       jobs:
         - glanceclient-dsvm-functional-py3
-    post:
-      jobs:
-        - openstack-tox-cover