Segregate the VSM calls from database calls in N1kv plugin

Rearrange the code in such a way that the calls to the VSM are
outside the database session. This avoids DB locks on n1kv tables.

Conflicts:
	neutron/plugins/cisco/n1kv/n1kv_neutron_plugin.py

Change-Id: Ic0f0d816cca06a3b03fdd9b58ee7599ddf65473e
Closes-Bug: 1290646
(cherry picked from commit 1e210c7cc9d3d8dd6b3a72112dd8395cad4dc3a9)
Merge "Segregate the VSM calls from database calls in N1kv plugin" into stable/icehouse