https://github.com/Netflix/eureka/issues/59: Fix for the following issues

1) Eureka client tries to talk to a server in the same zone and fails over to the next server predictably for all clients in that zone. This could put a lot of pressure on the server that all these clients are failing over. These clients should distribute the load to other servers in the case of failover. This can be achieved by choosing a different failover server depending on the client.

2) Currently when there are 2 servers in the same zone, the eureka client always chooses the same server every time. The second server is not utilized until failover. This restricts the ability to loadbalance requests across multiple servers in the same zone.