Comment 16 for bug 1724114

Reviewed: https://review.opencontrail.org/39893
Committed: http://github.com/Juniper/contrail-controller/commit/6f8d7b4ae781157a034a785934ede0c4fc753a61
Submitter: Zuul (<email address hidden>)
Branch: R3.1

commit 6f8d7b4ae781157a034a785934ede0c4fc753a61
Author: Manish <email address hidden>
Date: Tue Feb 20 12:21:52 2018 +0530

FMG label missed.

Transiently FMG label can be assigned to multiple tree, because of control node
restarts or flaps. In this case say tree-1 is using label A and it was supposed
to be withdrawn or staled. Re-use of label happens at CN and is assigned to
tree-2. XMPP messages for withdrawal of label A from tree-1 and adding to tree-2
can go in any order. So add for tree-2 is seen before withdrawal in problematic
case. This results in label A removed even though tree-2 is active user.

Solution:
Maintain a list of users for label. Label remains intact till list is not empty.
In above case tree-2 will be present in list even after tree-1 is withdrawn and
label remains intact.

Change-Id: Ia2bb22d0c958355a5c2295709fd5eb90c1a79a65
CLoses-bug: #1724114