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
Merge "Allow nvp_api to load balance requests"
Remove relative imports from NVP plugin

The majority of relative imports in the nvp plugin will be fixed in
blueprint nvp-api-client-loadbalance-request. This patch removes the
rest of them in and moves the vim tabstop line to the top of the
header file to be consistent with the rest of the files in quantum.
Fixes bug 1091596

Change-Id: I6c8299ca73ae5df75c87f302680908f863f81f02