Ranger Agent add tag and push of latest

Latest tag is not auto-updated by quay,
so this puts support to tag ranger-agent
image as latest each time an image is pushed
to quay.io.

Change-Id: I3e28017d315356ed24653292159307a5a58a617b

.zuul.yaml

@@ -8,6 +8,8 @@
       jobs:
         - openstack-tox-pep8
         - openstack-tox-py36
+    promote:
+      jobs:
         - ranger-agent-image-publish
 
 - job:

Makefile

@@ -15,7 +15,6 @@
 DOCKER_REGISTRY            ?= quay.io
 IMAGE_NAME                 ?= ranger-agent
 IMAGE_PREFIX               ?= attcomdev
-IMAGE_TAG                  ?= ocata
 HELM                       ?= helm
 LABEL                      ?= commit-id
 COMMIT                     := $(shell git rev-parse HEAD)
@@ -65,6 +64,8 @@ endif
 
 ifeq ($(PUSH_IMAGE), true)
 	docker push $(IMAGE)
+	docker tag $(IMAGE) ${DOCKER_REGISTRY}/${IMAGE_PREFIX}/${IMAGE_NAME}:latest
+	docker push ${DOCKER_REGISTRY}/${IMAGE_PREFIX}/${IMAGE_NAME}:latest
 endif
 
 .PHONY: clean