mongo-sync: Fix _mongo_sync_connect_replace().
mongo-sync: Fix _mongo_sync_connect_replace().

Do not copy the ReplicaSet structure from the new connection to the
old - we'll end up in an infinite loop if we do so. Set them to NULL
in the old, and free them in the new instead.

algernon/libmongo-client,algernon/libmongo-client,algernon/libmongo-client