JAVA-1160: ClusterDescription.getAny now returns any ok server, not just primaries and secondaries.  A new method, getAnyPrimaryOrSecondary, has been added for server selectors that will only talk to primaries or secondaries.
JAVA-1161: When a replica set member returns an empty list of hosts, assume it's not a part of an initiated replica set and do not remove every server from the client view of the replica set.
JAVA-1159: If the connection wasn't already null, retry once before declaring a server down.