[Nut-upsdev] Changes to 'upsdrvctl'

[Arjen de Korte]

The change of the PID file names for the drivers causes some problems
when upgrading from a previous version of NUT. The new 'upsdrvctl' will
not be able to find the PID from drivers started by a previous version
(since it looks for the new names only). To prevent shooting ourselves
in the foot when upgrading, I slapped together a 'status' function in
'upsdrvctl' to see whether we can find a PID for a running driver. In
case of an upgrade from an older version (using the old naming scheme)
to the new one, this will obviously fail. This is what we want, since
trying to stop the old one, failing to do so and consequently, failing
to restart 'upsd' too is probably not something we like to do. In that
case, it is probably better to warn about this possibility beforehand
and keep the old driver and old upsd running.

Regards, Arjen