LACP upgrade - 6: updating member port aggregator attach handler

Updated #member #port #attach #handler with the aggregator in the #LACP module. This handler make the #hardware calls to #attach the member port with the selected aggregator and mark the member port state as attached. The #remote #peer is informed of this by sending a #new #LACP #PDU and peer is marked as #synchronized. Later, when peer responds with it's PDU the actual #distribution and #collection operations will be #started for member ports. On attaching the member port with the aggregator the LAG distribution and collection operations will be started in hardware. i.e. The traffic sent out on the aggregator port will be distributed to the member ports and traffic received on the member ports will be collected on to the combined aggregator port.

#LACP update 19 ...
[commit c4c8b0875ce3ca180a3982e850131b58f15a1451] (https://github.com/nes-repo/NES-Open-Switch/commit/c4c8b0875ce3ca180a3982e850131b58f15a1451)