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)
fixes tests using called_once_ without assert

A few tests were using mock's called_once, or called_once_with_args
instead of assert_called_once or assert_called_once_with_args. Those
methods return a bool that needs to be actively checked.

The tests are fixed to avoid them from passing if the call condition
is not met.

Change-Id: I21e5257b26b2a08cc8f0b108233d1d5cc0b97b89
Closes-bug: #1297875
(cherry picked from commit c6c4a20777921dc1b21e80edb96ccd957a054c68)
use floatingip's ID as key instead of itself

Change-Id: I267f174a0e2e611ec007404c7b44e2c73a359c38
Closes-Bug: 1294526
(cherry picked from commit 7120325d37df414d8de084c5b41fdfbea3a06565)
Set ns_name in RouterInfo as attribute

Closes-Bug: #1302007
Change-Id: I02a9b92eea06010569d3d9c5a987e69f89b23be5
(cherry picked from commit ceee7b4ac9d027499dfd2568868f1192bfb77879)
Merge "fixes tests using called_once_ without assert" into milestone-proposed
Merge "use floatingip's ID as key instead of itself" into milestone-proposed
Merge "Set ns_name in RouterInfo as attribute" into milestone-proposed
Merge "Add missing DB migrations for BSN ML2 plugin" into milestone-proposed