bash completion for container labels to `service {create,update}`

Signed-off-by: Harald Albers <github@albersweb.de>
(cherry picked from commit 13c138ec2a896a87da8fa81693975e7ffbec85fd)
Signed-off-by: Tibor Vass <tibor@docker.com>

contrib/completion/bash/docker

@@ -1741,6 +1741,7 @@ _docker_service_update() {
 
 	if [ "$subcommand" = "create" ] ; then
 		options_with_args="$options_with_args
+			--container-label
 			--mode
 		"
 
@@ -1754,6 +1755,8 @@ _docker_service_update() {
 	if [ "$subcommand" = "update" ] ; then
 		options_with_args="$options_with_args
 			--arg
+			--container-label-add
+			--container-label-rm
 			--image
 		"