Add bash completion for `docker service {create,update} --tty`

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

contrib/completion/bash/docker

@@ -2629,6 +2629,7 @@ _docker_service_update() {
 
 	local boolean_options="
 		--help
+		--tty -t
 		--with-registry-auth
 	"