Use templates for cover and lower-constraints

Small cleanups:

* Use openstack-tox-cover template, this runs the cover job
  in the check queue only. Remove individual cover jobs.
* Use openstack-lower-constraints-jobs template, remove individual
  jobs.
* Sort list of templates

Fix cover job, $project is not expanded in tox.ini and thus the job
fails. Use "pycadf" instead.

Change-Id: I72da23a0d6c6b3cc87e66d94c419668fce66e704

.zuul.yaml

@@ -1,18 +1,11 @@
 - 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
-    check:
-      jobs:
-        - openstack-tox-lower-constraints
-    gate:
-      jobs:
-        - openstack-tox-lower-constraints
-    post:
-      jobs:
-        - openstack-tox-cover

tox.ini

@@ -21,7 +21,7 @@ commands = python setup.py build_sphinx
 [testenv:cover]
 basepython = python3
 setenv =
-    PYTHON=coverage run --source $project --parallel-mode
+    PYTHON=coverage run --source pycadf --parallel-mode
 commands =
     stestr run '{posargs}'
     coverage combine