make sure we close the db we open

A test intentionally causes an exception to be raised and this was
causing tearDown to fail on windows.

src/ZODB/tests/testConfig.py

@@ -33,13 +33,15 @@ def tearDown(self):
 
     def _test(self, s):
         db = self._opendb(s)
-        self.storage = db._storage
-        # Do something with the database to make sure it works
-        cn = db.open()
-        rt = cn.root()
-        rt["test"] = 1
-        transaction.commit()
-        db.close()
+        try:
+            self.storage = db._storage
+            # Do something with the database to make sure it works
+            cn = db.open()
+            rt = cn.root()
+            rt["test"] = 1
+            transaction.commit()
+        finally:
+            db.close()
 
 
 class ZODBConfigTest(ConfigTestBase):