Cisco plugin check for a valid nexus driver
Cisco plugin check for a valid nexus driver

The Cisco plugin model should check for a valid Nexus driver before performing any
operations on hardware nexus devices.

Change-Id: Ib7760cc7bb24e2c7f6692cbd8274aefa71dc21a1
Fixes: Bug #1202822

hareeshpc/networking-cisco,Gitweijie/first_project,cisco-openstack/networking-cisco,cisco-openstack/networking-cisco,openstack/networking-cisco,noironetworks/networking-cisco,openstack/networking-cisco,nikolay-fedotov/networking-cisco,CiscoSystems/networking-cisco,Gitweijie/first_project,Tehsmash/networking-cisco,Tehsmash/networking-cisco,hareeshpc/networking-cisco,CiscoSystems/networking-cisco,noironetworks/networking-cisco