openqa/worker: make createhdds git branch to use configurable

So we can test non-master branches on stg easier. May extend this
design to other repos (like the tests...) later.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

roles/openqa/worker/defaults/main.yml

@@ -1,2 +1,3 @@
 openqa_hostname: localhost
 openqa_repo: updates
+openqa_createhdds_branch: master

roles/openqa/worker/tasks/createhdds.yml

@@ -1,5 +1,7 @@
-# Required vars
-# (none)
+# Required vars with defaults
+# - openqa_createhdds_branch
+##       string - The git branch of createhdds to check out
+##       default - master
 
 - name: Install required packages
   package:
@@ -32,8 +34,9 @@
 
 - name: Check out createhdds
   git:
-    repo: https://pagure.io/fedora-qa/createhdds.git # noqa 401
+    repo: https://pagure.io/fedora-qa/createhdds.git
     dest: /root/createhdds
+    version: "{{ openqa_createhdds_branch }}"
 
 - name: Set up createhdds cron job
   copy: src=createhdds dest=/etc/cron.daily/createhdds owner=root group=root mode=0755