AF_PACKET and RHEL7

A patch for ixgbe has been pushed upstream. Estimated fix is q3 2017 in RH7.4. It may make it earlier.

Those interested in running AF_PACKET in the meantime are free to send me an offlist email on how to get this running. Performance exceeds that of pf_ring from test data on a 6 Gb/s link, so we internally will at least be moving to it.