Add openvpn docker image and zuul job

Change-Id: I33c41ca6f582ac1c2208ef5cfa15cd852516a4f2

openvpn/Dockerfile

@@ -0,0 +1,4 @@
+FROM debian:10-slim
+RUN apt-get update && \
+    apt-get install --no-install-recommends -y openvpn && \
+    apt-get clean all

zuul.d/openvpn.yaml

@@ -0,0 +1,31 @@
+- job:
+    name: docker-images:build:openvpn
+    parent: vexxhost-build-docker-image
+    provides: docker-images:image:openvpn
+    vars: &id001
+      docker_images:
+      - context: openvpn/
+        repository: vexxhost/openvpn
+    files: &id002
+    - ^openvpn/.*
+- job:
+    name: docker-images:upload:openvpn
+    parent: vexxhost-upload-docker-image
+    provides: docker-images:image:openvpn
+    vars: *id001
+    files: *id002
+- job:
+    name: docker-images:promote:openvpn
+    parent: vexxhost-promote-docker-image
+    vars: *id001
+    files: *id002
+- project:
+    check:
+      jobs:
+      - docker-images:build:openvpn
+    gate:
+      jobs:
+      - docker-images:upload:openvpn
+    promote:
+      jobs:
+      - docker-images:promote:openvpn