Better interval behavior.

If no runqueue is supplied on which to prune sessions, we don't schedule a
session pruner, rather than scheduling a long running database action on the
Interval timer thread, thereby booching all other Intervals.

src/main/java/com/samskivert/servlet/user/UserManager.java

@@ -124,7 +124,8 @@ public class UserManager
         }
 
         // register a cron job to prune the session table every hour
-        _pruner = new Interval() {
+        if (pruneQueue != null) {
+            _pruner = new Interval(pruneQueue) {
                 @Override public void expired () {
                     try {
                         _repository.pruneSessions();
@@ -133,17 +134,17 @@ public class UserManager
                     }
                 }
             };
-        if (pruneQueue != null) {
-            _pruner.setRunQueue(pruneQueue);
-        }
             _pruner.schedule(SESSION_PRUNE_INTERVAL, true);
         }
+    }
 
     public void shutdown ()
     {
         // cancel our session table pruning thread
+        if (_pruner != null) {
             _pruner.cancel();
         }
+    }
 
     /**
      * Returns a reference to the repository in use by this user manager.