DOCS-747: adding admonition about localhost replica sets

Author: Sam Kleinman

source/tutorial/deploy-replica-set.txt

@@ -93,6 +93,12 @@ The examples in this procedure create a new replica set named ``rs0``.
 
       mongo localhost:27017
 
+   .. note::
+
+      In a replica set, *all* members of the set must use
+      ``localhost`` addresses or *no* members of the replica set can
+      use the ``localhost`` addresses.
+
 #. Use :method:`rs.initiate()` to initiate a replica set consisting of
    the current member and using the default configuration: