Make LoadBalancer not extend Configurable interface

On master, LoadBalancer has a setClusterInfoProvider method and on branch-2, LoadBalancer has a setMasterServices method. Both ClusterInfoProvider and MasterServices could give a Configuration out so I do not think we need to expose another setConf method.

When refactoring StochasticLoadBalancer, the initialization order is also a pain as after setConf, we will load a lot of configuration but at that time, the ClusterInfoProvider is not present, and easy to cause NPE...

And it could also help simplity locking.