Provide a tempest-gabbi job, testing by tempest-gabbi

For sake of testing this uses the gabbits from placement,
so that there are some remote gabbits to experiment with.

The name follows the pattern set in the parent tempest jobs.

Depends-On: https://review.openstack.org/601614
Depends-On: https://review.openstack.org/607507
Change-Id: I7a9efefb28e23bf47951617cbe08f177235688d6

.zuul.yaml

@@ -1,3 +1,27 @@
 - project:
-    templates:
-      - noop-jobs
+    check:
+      jobs:
+        - tempest-gabbi
+    gate:
+      jobs:
+        - tempest-gabbi
+
+- job:
+    name: tempest-gabbi
+    parent: devstack-tempest
+    description: |
+      A job that can be used as a base for running gabbi tests
+      against a set of directories.
+    required-projects:
+      - openstack/gabbi-tempest
+    vars:
+      # Using placement as a known location, for sake of testing.
+      # If this works, then gabbi-tempest works.
+      gabbi_tempest_path: "{{ devstack_base_dir|default('/opt/stack') }}/placement/gate/gabbits"
+      tox_envlist: all
+      tempest_test_regex: 'gabbi'
+      # run test in serial, because we have no control over stestr group_regex
+      tempest_concurrency: 1
+      devstack_localrc:
+        TEMPEST_PLUGINS: "{{ devstack_base_dir|default('/opt/stack') }}/gabbi-tempest"
+        USE_PYTHON3: True