tests/thread: Make thread_exc2 runable on baremetal.

tests/thread/thread_exc2.py.exp

 Unhandled exception in thread started by <function thread_entry at 0x\[0-9a-f\]\+>
 Traceback (most recent call last):
-  File "thread/thread_exc2.py", line 6, in thread_entry
+  File \.\+, line 6, in thread_entry
 ValueError: 
 done