Merge rev 38773 from 3.4 branch.

tpc_abort():  Repair fubar'ed "repaired" logic.

src/ZODB/BaseStorage.py

@@ -189,11 +189,13 @@ class BaseStorage(UndoLogCompatible):
         try:
             if transaction is not self._transaction:
                 return
+            try:
                 self._abort()
                 self._clear_temp()
                 self._transaction = None
             finally:
                 self._commit_lock_release()
+        finally:
             self._lock_release()
 
     def _abort(self):