try to fix thread bug
try to fix thread bug

linked to http://jira.canaltp.fr/browse/NAVITIAII-2047

the import of _strptime does not seems to be thread safe
(http://bugs.python.org/issue7980), so it has to be done before threads
start.

Hoshiyo/fabric_navitia,Hoshiyo/fabric_navitia,Hoshiyo/fabric_navitia,CanalTP/fabric_navitia,CanalTP/fabric_navitia