My ubuntu is slow to shutdown, and the culprits seem to be modemmanager and something called nm-dispatcher.action.

On shutdown I get a message on the terminal saying something like "asking all remaining processes to terminate" and then there is a ~5 second delay, before unresponsive processes are forcibly killed.

One of them was modem-manager, and I don't have a modem so I fixed that one with simply sudo apt-get remove modemmanager and there doesn't appear to be any side effects.

The other one is something like "nm-dispatcher.action: Caught signal 15, shutting down. ..." which I was able to fix by removing network-manager and network-manager-gnome. But then, obviously, I don't get the network manager icons and stuff which I need in gnome-shell. I have tried wicd as a replacement, but it is not working to my liking.

So how can I prevent those processes from hanging during shutdown?