Fixed concurrency problem.

git-svn-id: http://svn.igniterealtime.org/svn/repos/messenger/trunk@2900 b35dd754-fafc-0310-a699-88a17e54d16e

src/java/org/jivesoftware/messenger/SessionManager.java

@@ -453,7 +453,7 @@ public class SessionManager extends BasicModule {
             if (sessions == null || sessions.isEmpty()) {
                 // First session from the remote server to this server so create a
                 // new association
-                List<IncomingServerSession> value = new ArrayList<IncomingServerSession>();
+                List<IncomingServerSession> value = new CopyOnWriteArrayList<IncomingServerSession>();
                 value.add(session);
                 incomingServerSessions.put(hostname, value);
             }