Remove hello-world:latest tag before integration

This is to make sure we are in the same state on linux/arm, linux/… and
other architecture.

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

hack/make/.ensure-frozen-images

@@ -97,5 +97,6 @@ case "$DOCKER_ENGINE_OSARCH" in
 		;;
 	*)
 		docker tag hello-world:latest hello-world:frozen
+		docker rmi hello-world:latest
 		;;
 esac