Added temp_value to RRDDataSource to store values. Useful for rrd update.
Added temp_value to RRDDataSource to store values. Useful for rrd update.

netgroup/OSHI-monitoring,ferrarimarco/OSHI-monitoring,StefanoSalsano/OSHI-monitoring,StefanoSalsano/OSHI-monitoring,ferrarimarco/OSHI-monitoring,netgroup/OSHI-monitoring