cells: Further refine LoginManager startup and shutdown

Addresses flaws in server socket recreation in case of failures,
makes the code more DRY, uses thread pool for rejected connections,
kills children early, and waits for them to die before terminating
the login cell factory, removes legacy socket shutdown hack.

Target: trunk
Require-notes: no
Require-book: no
Acked-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Patch: http://rb.dcache.org/r/6326/

modules/cells/src/main/java/dmg/cells/nucleus/CellNucleus.java

@@ -588,6 +588,21 @@ public void  threadGroupList() {
 
 
 
+    /**
+     * Blocks until the given cell is dead.
+     *
+     * @throws InterruptedException if another thread interrupted the
+     * current thread before or while the current thread was waiting
+     * for a notification. The interrupted status of the current
+     * thread is cleared when this exception is thrown.
+     * @return True if the cell died, false in case of a timeout.
+     */
+    public boolean join(String cellName)
+        throws InterruptedException
+    {
+        return __cellGlue.join(cellName, 0);
+    }
+
     /**
      * Blocks until the given cell is dead.
      *