N1kv: Fixes fields argument not None

N1kv plugin includes 'fields' in call to get_<resource> function in
superclass. This can trigger errors if other fields are used in the
subsequent processing in the N1kv plugin's own get_<resource>
function.

Change-Id: I63687a830579a178c6daaa2b8f71bef7eb53d584
Closes-bug: #1285289
Fix ml2 db migration of subnetroutes table

The ml2 db migration path doesn't create subnetroutes table. Therefore
installations were partially relying on automatic schema generation.

This patch fixes the migration path.

Change-Id: I3060dd9538b629ad7277af28008ddde27926dcc4
Closes-Bug: #1290255
Merge "N1kv: Fixes fields argument not None"
Merge "Fix ml2 db migration of subnetroutes table"