Add missing DB migrations for BSN ML2 plugin

Adds missing database migrations for the Big Switch
ML2 driver and plugin.

Closes-Bug: #1298459
Change-Id: I6a46a53e069353501d85c4c8400f98514d6f0162
(cherry picked from commit d3be7b040eaa61a4d0ac617026cf5c9132d3831e)
Set ns_name in RouterInfo as attribute

Closes-Bug: #1302007
Change-Id: I02a9b92eea06010569d3d9c5a987e69f89b23be5
(cherry picked from commit ceee7b4ac9d027499dfd2568868f1192bfb77879)
Merge "Set ns_name in RouterInfo as attribute" into milestone-proposed
Merge "Add missing DB migrations for BSN ML2 plugin" into milestone-proposed