Retain NAPT Switch after Upgrade for SNAT

Retain NAPT Switch after Upgrade for SNAT

Test Scenario1: All OVS are connected back after upgrade.

1) Take the back-up of the Config DS and bring down the controller.
2) Disconnect OVS(by blocking port 6640 & 6653)
3) Upgrade ODL, set upgrade-flag=true and reload the config DS.
4) Start connecting back the OVS with first connecting non-napt
switches followed by Napt-Switches.
5) set upgrade-flag=false once all the OVS are connected by to ODL.
6) Verify earlier Napt Switches continues to work as Napt Switches
and all earlier on-going SNAT session and new sessions are not
impacted.

Test Scenario2: Few OVS(which are elected as Napt) are not
connected back after upgrade.

1) Take the back-up of the Config DS and bring down the controller.
2) Disconnect OVS(by blocking port 6640 & 6653)
3) Upgrade ODL, set upgrade-flag=true and reload the config DS.
4) Start connecting back the OVS with first connecting non-napt
switches and do not connect few OVS elected as Napt Switches earlier.
5) set upgrade-flag=false.
6) Verify a new Napt Switch is elected for those router whose Napt
Switches are not been connected back after upgrade.
7) Verify new SNAT sessions are established and earlier on-going SNAT
session gets migrated to newly elected Napt Switch.

JIRA: NETVIRT-1222

Change-Id: I194124596e987c43703be37707235a6c88c91013
Signed-off-by: xcheara <chetan.arakere@altencalsoftlabs.com>
Signed-off-by: shaik <shaik.b@altencalsoftlabs.com>
Signed-off-by: xcheara <chetan.arakere@altencalsoftlabs.com>