Don't open data files again if the store has been closed.. on windows tests were failing since the open data files could not be deleted.

git-svn-id: https://svn.apache.org/repos/asf/incubator/activemq/trunk@396583 13f79535-47bb-0310-9956-ffa450edef68

activemq-core/src/main/java/org/apache/activemq/kaha/impl/KahaStore.java

@@ -183,6 +183,8 @@ public class KahaStore implements Store{
     }
 
     protected synchronized void initialize() throws IOException{
+    	if( closed )
+    		throw new IOException("Store has been closed.");
         if(!initialized){
             initialized=true;
             directory=new File(name);