Create a Scheduler client library

In order to split the scheduler code, a new library needs to be
created as a client for other Nova components.
Direct calls to conductor for updating stats in ResourceTracker
need to be decoupled into this library.

Change-Id: Ifcfeb90e09a75fc25ac5fd4f18cfd69ea0b21f50
Implements: blueprint scheduler-lib
Merge "Create a Scheduler client library"