Fix l2 pop doesn't propagate ip address updates

Propagates ip address changes when an ip address is :
added, removed, or changed.
Add a new rpc call for the updates of forwarding informations.

Fixes: Bug #1234137
Change-Id: Ib5b971bd02f20a0ea73f88ce9685e944226bb5a2
Fix downgrade in migration

In folsom_initial name of table nexusport_bindings to drop was not
correct.

Change-Id: Icb805f3e06c4e05708d11927b24a494c8cc7944f
Merge "Fix l2 pop doesn't propagate ip address updates"
Merge "Fix downgrade in migration"