Resource issues with plugin

[smanpathak]

We recently used opencontrail plugin for neutron for a customer integration. Found following issues --

0. It makes a separate http request call to Opencontrail controller for each fetch. This causes the plugin to churn through a lot of connections for simple requests. It should make use of http sessions to reuse connections. In our environment, a connection is made through a tunnel and has non-trivial costs.
1. It does not have a DB cache. It always calls opencontrail controller for any data. This effectively just adds delay in retrieving opencontrail data. Also, in cases where controller could be down/unreachable views in Openstack break. Ideally, it should keep this information in a plugin specific database.