Add ensure-pip to osh-gate-runner for addons

This change adds the ensure-pip task to the gate-runner in order
to ensure that the various jobs we run will have pip by default.

Change-Id: I0a045a3e12ede8480d47a79dc60789be4a7054d3

tools/gate/playbooks/osh-gate-runner.yaml

@@ -12,6 +12,9 @@
 
 - hosts: primary
   tasks:
+    - name: Ensure pip
+      include_role:
+        name: ensure-pip
     - name: Run gate scripts
       include_role:
         name: osh-run-script