Refined multihoming test cases

Added forwarding strategy as an input argument.
Minor changes to CongestionAware

Minor changes to CongestionAware forwarding strategy: in AIMD adjustment of the virtual congestion window, MD by 0.8 instead of half.
Refined multihoming test cases

Added competing flows to multihoming-two test case to evaluate fairness.
Restored ConsumerWindowRelentless
Added ConsumerWindowRelentless to all test cases
Modified CongestionAware forwarding strategy

Instead of maintaining virtual congestion window, just record the NACK ratio.