Be less harsh and just log a warning in case some shutdown methods rely on posted events or messages being silently ignored (invoker still throws however, because it was throwing before)

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5492 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/server/net/ConnectionManager.java

@@ -857,7 +857,7 @@ public class ConnectionManager extends LoopingThread
     void postMessage (Connection conn, DownstreamMessage msg)
     {
         if (!isRunning()) {
-            throw new IllegalStateException("Connection manager has been shutdown");
+            log.warning("Posting message to inactive connection manager", new Exception());
         }
         
         // sanity check