Allow nvp_api to load balance requests

Allow nvp_api to load balance requests

The current version of the nvp_api client does not load balance
requests across multiple controllers. Instead, it just sends all the requests
to one controller and if there is a controller failure it will failover
to use another controller. This blueprint implements the ablility to
utilize all controllers at once.

blueprint nvp-api-client-loadbalance-request

Change-Id: I331be2a23ae360a95786152d5f116359f690d9f3