Comment 14 for bug 1611881

Reviewed: https://review.opencontrail.org/23622
Committed: http://github.org/Juniper/contrail-controller/commit/68b8416638340ac90a50417d895e4c65709bd9d3
Submitter: Zuul
Branch: R3.0

commit 68b8416638340ac90a50417d895e4c65709bd9d3
Author: Prabhjot Singh Sethi <email address hidden>
Date: Thu Aug 11 16:35:52 2016 +0530

Fix flows stuck in vrouter for ever

Issue:
------
Stats collector and flow processing run in parallel
so flow handle and gen id not being the key can change
while stats collector aging process, due to which it
can run eviction validation using old flow handle and
gen id, while enqueue an eviction request using new
flow handle and gen id, resulting in skipping delete
from vrouter and causing lingering flows

Fix:
----
Lock and fetch flow handle and gen idat the start of
eviction processing and use the same while enqueuing
eviction request

Closes-Bug: 1611881
Change-Id: I9c7aa4bfee0b82334e92d5a748d1b2045e3976df
(cherry picked from commit 52ffcdbdde5b32a7c868c59dd370b13e827ea96f)