Fix for failing network operations in Cisco plugin

Fix for failing network operations in Cisco plugin

Bug #1050545

This fixes the exceptions occurring in the virtual switch mode of the
Cisco plugin for create/delete/update network operations. The exceptions
were occurring on account of the recent changes in the OVS module to the
get_vlan and get_vlans methods, which were still being invoked here.
Test configuration has been changed to increase the code coverage to
catch such issues in the future. All changes are limited to the Cisco
plugin and related tests.

Change-Id: Id18473f7a9a2a22217a59b4f8b1541b4918e07e7