fix(auth): prevent stalling on authentication when connected
fix(auth): prevent stalling on authentication when connected

ReplicaSet was storing the authentication call in the disconnectHandler
when it didn't need to, leading to auth stalling. From now on, will
only store handlers if ReplSet is not actually connected.

NODE-1402

mongodb/node-mongodb-native,mongodb/node-mongodb-native,mongodb/node-mongodb-native,mongodb/node-mongodb-native