Dear Maintainer,

If lxc is uinstalled, its initscripts fail with an error code instead of
exiting quitely as required by Debian policy 9.3.2:

  startpar: service(s) returned failure: lxcfs lxc lxc-net ... failed!

The usual way to handle this is with a quick check for the presence of the
relevant executable near the start and calling 'exit 0' if not present.

Thanks,

Andrew