Add bash completion for managing ports in services

Bash completion for

- `docker service create --port`
- `docker service update --port-{add,rm}`

Signed-off-by: Harald Albers <github@albersweb.de>

contrib/completion/bash/docker

@@ -2656,6 +2656,7 @@ _docker_service_update() {
 			--hostname
 			--mode
 			--name
+			--port
 		"
 
 		case "$prev" in
@@ -2687,6 +2688,8 @@ _docker_service_update() {
 			--group-add
 			--group-rm
 			--image
+			--port-add
+			--port-rm
 		"
 
 		case "$prev" in