Use oneiric for stable/diablo.

For all python27 jobs, use oneiric slaves if the branch is
stable/diablo.  Python26 jobs are already on oneiric due to
lack of python 2.6 on anything later.

Change-Id: Id440e14721ccdd4225c5e5b170510c3c000a36b3

templates/python_jobs.yml

@@ -116,6 +116,12 @@ logrotate:
   artifactDaysToKeep: -1
   artifactNumToKeep: -1
 
+parameters:
+  - name: NODE_LABEL
+    description: Label of node to use for this build
+    type: label
+    default: '@NODE@'
+
 triggers:
   - zuul