Excessive Blacklisting when using a load balancer to access nodes

When using a single, load balancer server to connect to nodes and node failures occur, the current RoundRobinServerManager will blacklist the single server and return "No connection could be made because all servers have failed" instead of actually trying to reconnect to the load balancer and receiving a working node.

I added a SingleServerManager (thanks to Nick for the pointers) that will always return the server and never blacklist.

-Nathan