[IMP] Prevent unclosed cursor during tests

If an error happens in an overload of setUp, the already-open cursor
is likely not to get properly released before the next test,
deadlocking the db, because tearDown only runs if setUp has
succesfully completed.

Cleanups were added specifically to run every time, after tearDown has
(potentially) been executed.

closes #8327

Note: cleanups run in LIFO order (as they should).

openerp/tests/common.py

@@ -94,9 +94,10 @@ class TransactionCase(BaseCase):
         TransactionCase.cr = self.cursor()
         TransactionCase.uid = openerp.SUPERUSER_ID
 
-    def tearDown(self):
-        self.cr.rollback()
-        self.cr.close()
+        @self.addCleanup
+        def close_cursor():
+            self.cr.rollback()
+            self.cr.close()
 
 
 class SingleTransactionCase(BaseCase):