Not sure that it is possible. In HM config it is defined as:
# grep packets /usr/local/psa/admin/conf/health-config.xml
<device name="lo" dbname="interface/if_packets-lo.rrd" monitor="false"/>
<device name="venet0" dbname="interface/if_packets-venet0.rrd" monitor="true"/>
And there are following:
# ll /usr/local/psa/var/health/data/localhost/interface/
total 1992
-rw-r--r-- 1 root root 336060 Nov 25 13:29 if_errors-lo.rrd
-rw-r--r-- 1 root root 336060 Nov 25 13:34 if_errors-venet0.rrd
-rw-r--r-- 1 root root 336060 Nov 25 13:29 if_octets-lo.rrd
-rw-r--r-- 1 root root 336060 Nov 25 13:29 if_octets-venet0.rrd
-rw-r--r-- 1 root root 336060 Nov 25 13:34 if_packets-lo.rrd
-rw-r--r-- 1 root root 336060 Nov 25 13:34 if_packets-venet0.rrd