Bring over some link aggregation / LACP protocol improvements and debugging
additions.

* Add some new tracing events to aid in debugging.
* Add in a debugging mode to drop transmit and received frames, specifically
  to test whether seeing or hearing heartbeats correctly cause LACP to
  drop the port.
* Add in (and make default) a strict LACP mode, which requires the
  heartbeat on a port to be heard before it's used.  Sometimes vendor ports
  will hang but the link layer stays up, resulting in hung traffic.
* Add logging the number of link status flaps, again to aid in debugging
  badly behaving switch ports.
* Calculate the lagg interface port speed as the multiple of the
  configured ports, rather than the largest.

Obtained from:	Netflix
MFC after:	2 weeks