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