As per defect:
   the "VNF packets dropped" time series is negative - negative number of packets dropped
   is not meaningful.
Solution:
   Return a positive value.
Change-Id: I358006a691f2d6b5954333b9f7a745aba97ae44f
Signed-off-by: Daniel Martin Buckley <daniel.m.buckley@intel.com>
 
         result = {
             "packets_in": tx_total,
-            "packets_dropped": (tx_total - rx_total),
+            "packets_dropped": abs(rx_total - tx_total),
             "packets_fwd": rx_total,
             # we share ProxResourceHelper with TG, but we want to collect
             # collectd KPIs here and not TG KPIs, so use a different method name