LAG upgrade - 7: aggregator framework update

Updated #aggregator #framework in accordance with the #data-structure #changes in LAG module. Updated the aggregator #create / #remove #routines according to the latest changes. Corrected the #indexing in the #agent #mapper routine.

#LAG update 15 ...
[commit 99c33261b9d71c7bfc1fcedd669ab4f71e6524a6] (https://github.com/nes-repo/NES-Open-Switch/commit/99c33261b9d71c7bfc1fcedd669ab4f71e6524a6)