Fix error in rock_status if ethtool -S lists string several times (#246)
Fix error in rock_status if ethtool -S lists string several times (#246)

* Fix error in rock_status if ethtool -S lists string several times
* use /sys/class/net/${interface}/statistics/ for if stats

rocknsm/SimpleRock,CyberAnalyticDevTeam/SimpleRock,CyberAnalyticDevTeam/SimpleRock,CyberAnalyticDevTeam/SimpleRock,rocknsm/SimpleRock,spartan782/rock,spartan782/rock,rocknsm/rock,rocknsm/rock,rocknsm/SimpleRock,spartan782/rock,rocknsm/rock