test adding and removing shared mcast dst tunnels

Adds and delete 2000 multicast vxlan tunnels sharing group address
to test mcast tunnel ref count code as part of the stability stage (before starting traffic tests)

Change-Id: Ic50cedf80471e14431feb493104eff5ea7d5d429
Signed-off-by: Eyal Bari <ebari@cisco.com>