Fix "System" user remaining authenticated on bootstrap thread.

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@3248 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/filesys/smb/server/repo/ContentDiskDriver.java

@@ -331,7 +331,8 @@ public class ContentDiskDriver implements DiskInterface, IOCtlInterface
                 {
                     logger.warn("Failed to rollback transaction", ex);
                 }
-            }                
+            }
+            authComponent.clearCurrentSecurityContext();
         }
 
         // Check if the client side drag and drop appliction has been enabled