Revert "Don't use opendev docker proxy"

This reverts commit 42f3b3eaf5.

Reason for revert: dockerhub now sets a hard limit on daily pulls, lets switch back to using the opendev docker proxy.

Change-Id: I87e399c89d5736f39d7bdba2011655e5f5766180

playbooks/osh-infra-gate-runner.yaml

@@ -20,6 +20,9 @@
       include_role:
         name: override-images
       when: buildset_registry is defined
+    - name: Use docker mirror
+      include_role:
+        name: use-docker-mirror
     - name: "creating directory for run artifacts"
       file:
         path: "/tmp/artifacts"