Contrail plugin should use caching database

[smanpathak]

Contrail plugin for neutron uses contrail server as source of truth and forwards all requests. This adds delays in serving neutron requests. Instead, the plugin should consider caching data locally and return based on cache.
NSX plugin for neutron as an example.

[gokulpch]

This is being tracked and the issue is with the manual installation of Memcached server. This will be packaged with the containers form the next release.