Use template for lower-constraints

Small cleanups:

* Use openstack-lower-constraints-jobs template, remove individual
  jobs.
* Sort list of templates

Change-Id: Id9e8f44d7c4d352682ca4df80f9470c7e6144509
Needed-By: https://review.openstack.org/623229

.zuul.yaml

@@ -71,21 +71,21 @@
 
 - project:
     templates:
-      - openstack-python36-jobs
+      - check-requirements
+      - nodejs4-jobs
+      - openstack-lower-constraints-jobs
       - openstack-python-jobs
       - openstack-python35-jobs
-      - publish-openstack-docs-pti
+      - openstack-python36-jobs
       - periodic-stable-jobs
-      - check-requirements
+      - publish-openstack-docs-pti
       - release-notes-jobs-python3
-      - nodejs4-jobs
     check:
       jobs:
         - horizon-openstack-tox-python3-django111
         - horizon-selenium-headless:
             voting: false
         - horizon-dsvm-tempest-plugin
-        - openstack-tox-lower-constraints
         - horizon-tox-bandit-baseline:
             voting: false
     gate:
@@ -93,4 +93,3 @@
       jobs:
         - horizon-openstack-tox-python3-django111
         - horizon-dsvm-tempest-plugin
-        - openstack-tox-lower-constraints