Rewrite previous commit in a way it does not break threaded tests

git-svn-id: https://svn.erp5.org/repos/neo/trunk@2832 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/storage/app.py

@@ -92,8 +92,10 @@ class Application(object):
         self.listening_conn = None
         self.nm.close()
         self.em.close()
-        if self.dm is not None:
+        try:
             self.dm.close()
+        except AttributeError:
+            pass
         del self.__dict__
 
     def _poll(self):

neo/storage/database/manager.py

@@ -30,9 +30,6 @@ class DatabaseManager(object):
         """
         self._under_transaction = False
 
-    def close(self):
-        pass
-
     def isUnderTransaction(self):
         return self._under_transaction