Improve Shutdown Logging (#610)

Don't attempt to journal an asyncio `CancelledError`, just reraise it.
This cleans up the shutdown procedure and avoids logging many spurious
errors.

Author: kraftp

dbos/_outcome.py

@@ -16,6 +16,7 @@
 
 from dbos._context import EnterDBOSStepRetry
 from dbos._error import DBOSException
+from dbos._logger import dbos_logger
 from dbos._registrations import get_dbos_func_name
 
 if TYPE_CHECKING:
@@ -184,6 +185,9 @@ async def _wrap(
         try:
             value = await func()
             return await asyncio.to_thread(after, lambda: value)
+        except asyncio.CancelledError:
+            dbos_logger.warning(f"Asyncio task cancelled for workflow or step {func}")
+            raise
         except BaseException as exp:
             return await asyncio.to_thread(after, lambda: Pending._raise(exp))