Issues connecting to MDS clusters when bootstrap node does not have kv

When running in MDS and when the SDK is used inside a server process, we need to handle the initial configuration better.

Off-the-brim proposal:
Now that we allow upgrading of an HTTP poller to a CCCP poller, we can maybe simply allow http:// connection strings which the server processes can use to connect, since essentially this is what they actually receive from ns_server when they are started (an http:// address back to ns_server).