MT#9643 upstream fix tm: safety catch inside t_check_trans()

There was a deadlock if t_check_trans() is called from request route called
from the FAILURE_ROUTE or BRANCH_FAILURE_ROUTE - FS#482
http://sip-router.org/tracker/index.php?do=details&task_id=482#comment1693

Change-Id: I0eab72699b655863fcd1182417abfd571fc8f057