Comment 28 for bug 1529829

Reviewed: https://review.opencontrail.org/17015
Committed: http://github.org/Juniper/contrail-controller/commit/30971c76849c5c587c96a54d9335fa90dcd09630
Submitter: Zuul
Branch: R2.21.x

commit 30971c76849c5c587c96a54d9335fa90dcd09630
Author: Manish <email address hidden>
Date: Fri Jan 15 08:56:00 2016 +0530

Multicast traffic gets dropped.

Problem:
When all the VMI's are gone multicast object is deleted. However VN is still not
gone and meanwhile new VMI gets added. During this window where all VMI were
gone to new VMI gets added, olist for replication tree is received from
control-node. This update is neglected in absence of multicast object for same.
This results in no multicast tree.

Solution:
Retain multicast object till two conditions are met:
- All VMIS are gone
- VN is no more in use by multicast.

Change-Id: Ica43ce9ed4951f644d9049b354e0764c860ef4d4
Closes-bug: 1529829