Comment 21 for bug 1456284

Reviewed: https://review.opencontrail.org/11304
Committed: http://github.org/Juniper/contrail-controller/commit/819b18b97c3d3fb2c3e42826d57009592bf6d252
Submitter: Zuul
Branch: R2.20

commit 819b18b97c3d3fb2c3e42826d57009592bf6d252
Author: Prabhjot Singh Sethi <email address hidden>
Date: Fri Jun 5 12:31:54 2015 +0530

ToR Agent OVSDB - performance on HA

Issue:
------
After the initial read from OVSDB server all the previous
VlanPortBindingsEntries are created as Stale entries,
later on subscribing to operDB all the entries start getting
converted from stale to non-stale, however the data remains
same, where OVSDB client not identifying no op keeps on
triggering updates on Physical Port entry, resulting in
preformance degradation

Fix:
----
Keep track of old_logical_switch_name in vlan port binding
entry and if on change it is a no op avoid triggering
updates to physical port entry

Partial-Bug: #1456284
Change-Id: I4a61904056ca374a34d40823f623fc14dfbcff67
(cherry picked from commit 363ef441a60121f55a3d3cccae3efac6899a81cd)