net: samples: pktgen mode samples/tests for qdisc layer

This adds samples for pktgen to use with new mode to inject pkts into
the qdisc layer. This also doubles as nice test cases to test any
patches against qdisc layer.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>