[collectd] Automatic reload of the lm_sensors configuration

[Staněk Luboš]

Hi Florian,
I am sending a series of three patches that update the sensors plugin to
respond to the lm_sensors' configuration change.

The plugin works the same way it did, only when it detects the
lm_sensors' configuration change, it throws away the old feature list
and reloads the updated sensors.conf.

It reports the 'reload' to syslog() so that the user has the positive
identification that the new configuration is reflected.

Best regards,
Lubos