fix: set _db_type to None when clearing anydbm db.

Author: rouilj

roundup/backends/sessions_dbm.py

@@ -46,6 +46,8 @@ def clear(self):
             os.remove(path+".dir")
             os.remove(path+".dat")
 
+        self._db_type = None
+
     def cache_db_type(self, path):
         ''' determine which DB wrote the class file, and cache it as an
             attribute of __class__ (to allow for subclassed DBs to be