Added basic tests for multicast vxlan tunnels

Added basic tests for multicast vxlan tunnels

unicast flood test - test headend replication
multicast flood test - test flooding when a multicast vxlan tunnel is present in BD
multicast receive test - verify that multicast packet are received on their
   corresponding unicast tunnels and that unmatched packets are dropped

all tests run after adding and removing 200 mcast tunnels to test stability

Change-Id: Ia05108c39ac35096a5b633cf52480a9ba87c14df
Signed-off-by: Eyal Bari <ebari@cisco.com>
(cherry picked from commit c4aaee11468aa5ed7af01d0747d912493cff002d)