Build and publish build images to Dockerhub

The build process of all the slaves images is taking a lot
of time. Shorten the cycle by building and publishing at
the same time.

Change-Id: I860ef0c85c2625b7d3ca657fdd352787364af61c
diff --git a/jenkins-docker/Makefile b/jenkins-docker/Makefile
index 5cfc193..bfafb17 100644
--- a/jenkins-docker/Makefile
+++ b/jenkins-docker/Makefile
@@ -7,8 +7,8 @@
 build clean publish:
 	for dir in $(ALL_DIRS); do (make NO_CACHE=$(NO_CACHE) -C $$dir $@) || exit 1; done
 
-build_slave:
-	for dir in $(SLAVE_DIRS); do (make NO_CACHE=$(NO_CACHE) -C $$dir build) || exit 1; done
+publish_slave:
+	for dir in $(SLAVE_DIRS); do (make NO_CACHE=$(NO_CACHE) -C $$dir build publish) || exit 1; done
 
 start stop restart:
 	make -C master $@