Restore rally job

Due to various changes in OpenStack and Rally CI, mistral-rally-task job
became broken.

Unfortunately, it took much time for Rally team to finish some
stuff(sorry for that) and migrate jobs for native Zuul V3 format.

This patch restores mistral-rally-task job which inherits from the job
which Rally team runs constantly on all inner patches.

Change-Id: Ia7177af9b3e1aaacf555f5c472c4f0471b796930

.zuul.yaml

@@ -28,18 +28,13 @@
 
 - job:
     name: mistral-rally-task
-    parent: mistral-devstack-base
-    run: playbooks/rally/run.yaml
+    parent: rally-task-mistral
     vars:
       devstack_plugins:
-        rally: https://git.openstack.org/openstack/rally
-      tox_environment:
-        DEVSTACK_GATE_TEMPEST_LARGE_OPS: 0
-        DEVSTACK_GATE_EXERCISES: 0
-        RALLY_SCENARIO: task-{{ zuul.project.canonical_name }}
-        DEVSTACK_GATE_NEUTRON: 1
+        rally-openstack: https://git.openstack.org/openstack/rally-openstack
+      rally_task: rally-jobs/task-mistral.yaml
     required-projects:
-      - openstack/rally
+      - openstack/rally-openstack
 
 - job:
     name: mistral-docker-buildimage
@@ -92,9 +87,7 @@
         # failures, please reach us on #tripleo IRC channel.
         - tripleo-ci-centos-7-scenario003-multinode-oooq
         - tripleo-ci-centos-7-scenario003-multinode-oooq-container
-        # Disable the rally job until it actually works
-        # - mistral-rally-task:
-        #     voting: false
+        - mistral-rally-task
     gate:
       jobs:
         - mistral-devstack
@@ -104,6 +97,7 @@
         - tripleo-ci-centos-7-scenario003-multinode-oooq
         - tripleo-ci-centos-7-scenario003-multinode-oooq-container
         - mistral-devstack-kombu
+        - mistral-rally-task
     post:
       jobs:
         - mistral-docker-buildimage:

playbooks/rally/run.yaml

@@ -1,12 +0,0 @@
-- hosts: all
-  tasks:
-    - name: Run Devstack
-      include_role:
-        name: run-devstack
-
-    - name: Run rally
-      shell:
-        cmd: |
-              ./tests/ci/rally-gate.sh
-        executable: /bin/bash
-        chdir: '{{ ansible_user_dir }}/src/{{ zuul.project.canonical_name }}/../rally'

rally-jobs/task-mistral.yaml

@@ -1,4 +1,4 @@
-{% set extra_dir = extra_dir or env["RALLY_EXTRA_DIR"] %}
+{% set extra_dir = "~/.rally/extra" %}
 ---
   MistralWorkbooks.list_workbooks:
     -