Currently the main loop creates an empty config and applies it to
force a shutdown of all of the existing configuration. While this is
functional and does avoid duplicating some code, it is also a bit
clunky and requires a special hack in the pidfile path handling
in the conf::apply method.
Instead, use a dedicated conf::shutdown method which tears down the
CTL ports and LUNs and closes the sockets.
Sponsored by: Chelsio Communications