JAVA-652: Synchronizing on correct object in close method

Author: jyemin

src/main/com/mongodb/util/SimplePool.java

@@ -155,14 +155,12 @@ private boolean permitAcquired(final long waitTime) throws InterruptedException
     }
 
     /** Clears the pool of all objects. */
-    protected void close(){
-        synchronized( _avail ){
-            _closed = true;
-            for ( T t : _avail )
-                cleanup( t );
-            _avail.clear();
-            _out.clear();
-        }
+    protected synchronized void close(){
+        _closed = true;
+        for (T t : _avail)
+            cleanup(t);
+        _avail.clear();
+        _out.clear();
     }
 
     public String getName() {