Bash completion for `docker node update` completes only one node

`docker node update` accepts only one node.
Before this change, bash completion would complete additional nodes.

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

contrib/completion/bash/docker

@@ -3522,7 +3522,11 @@ _docker_node_update() {
 			COMPREPLY=( $( compgen -W "--availability --help --label-add --label-rm --role" -- "$cur" ) )
 			;;
 		*)
-			__docker_complete_nodes
+			local counter=$(__docker_pos_first_nonflag '--availability|--label-add|--label-rm|--role')
+			if [ $cword -eq $counter ]; then
+				__docker_complete_nodes
+			fi
+			;;
 	esac
 }