Prevent peaks in traffic graph when restarting tor daemon.

For not losing current data, do:
cd /var/lib/munin/<DOMAIN>
mv <HOST>-tor_traffic-read-c.rrd <HOST>-tor_traffic-read-d.rrd
mv <HOST>-tor_traffic-written-c.rrd <HOST>-tor_traffic-written-d.rrd
rrdtool <HOST>-tor_traffic-read-d.rrd --data-source-type DERIVE
rrdtool <HOST>-tor_traffic-written-d.rrd --data-source-type DERIVE
Merge pull request #10 from onovy/master

Prevent peaks in traffic graph when restarting tor daemon.
For not losing current data, do:
cd /var/lib/munin/
mv <HOST>-tor_traffic-read-c.rrd <HOST>-tor_traffic-read-d.rrd
mv <HOST>-tor_traffic-written-c.rrd <HOST>-tor_traffic-written-d.rrd
rrdtool <HOST>-tor_traffic-read-d.rrd --data-source-type DERIVE
rrdtool <HOST>-tor_traffic-written-d.rrd --data-source-type DERIVE