OVSDriver: ignore set-field actions on nonexistent headers
OVSDriver: ignore set-field actions on nonexistent headers

vezril/ivs,rlane/ivs,harshsin/ivs,rlane/ivs,rlane/ivs,rlane/ivs,harshsin/ivs,vezril/ivs,floodlight/ivs,harshsin/ivs,vezril/ivs,floodlight/ivs,floodlight/ivs,harshsin/ivs