One or more VM entries getting removed after restarting DPN followed by controller restart

Hi,

Flows are getting removed from table 21.

Steps to Reproduce:

Assume: All flows were present and ping works well.

1. Shutdown controller.(Result: All flows removed in OVS).
2. Start controller again by running karaf and install VPN module.
3. Check ping work after controller restart.(it is successful)
4.Restart DPN and check flows. (Within few minutes most of the flows getting removed).

Result:

Ping between DPN stops working due to no flows in table 21.