charon-nm causes systemd to hang for a minute or two during system shutdown.

To reproduce:
- install strongswan
- create a networkmanager ipsec connection which uses strongswan
- bring up the ipsec connection. this starts charon-nm
- stop the ipsec connection. charon-nm is still running, even after the connection is stopped
- shut down the system. systemd hangs for a minute or two while stopping charon-nm

As a workaround, running "killall charon-nm" prior to shutdown prevents systemd from hanging.