nut: Fix nutmon issues with init

nut: Fix nutmon issues with init

NUT's upsmon is rather peculiar in that it has a child process that runs as
a regular user and a parent process that runs as root (in order to facilitate
shutting down the device if needed).  procd doesn't deal well with this and
doing 'normal' procd stop / restart / etc results in the child process still
hanging around but with not parent, which causes undesired behaviour.  Therefore,
add the use of 'upsmon -c stop' during process shutdown / restart in order to
ensure that upsmon is actually fully stopped.

Also fixes nut-monitor going into crashloop on network changes (due to
trigger that restarted upsmon but failed due to orphan child from before
restart).

Signed-off-by: Daniel F. Dickinson <redacted>