doc: clarify cluster behaviour with no workers

Fixes: https://github.com/nodejs/node/issues/1239
Ref: 41b75ca926
PR-URL: https://github.com/nodejs/node/pull/2606
Reviewed-By: bnoordhuis - Ben Noordhuis <info@bnoordhuis.nl>

doc/api/cluster.markdown

@@ -99,9 +99,10 @@ for things like sessions and login.
 Because workers are all separate processes, they can be killed or
 re-spawned depending on your program's needs, without affecting other
 workers.  As long as there are some workers still alive, the server will
-continue to accept connections.  Node.js does not automatically manage the
-number of workers for you, however.  It is your responsibility to manage
-the worker pool for your application's needs.
+continue to accept connections.  If no workers are alive, existing connections
+will be dropped and new connections will be refused.  Node.js does not
+automatically manage the number of workers for you, however.  It is your
+responsibility to manage the worker pool for your application's needs.
 
 ## cluster.schedulingPolicy