Catch asyncio.CancelledError during attempt tear-down (#88)

Author: igalshilman

python/restate/server_context.py

@@ -258,11 +258,12 @@ def safe_remove(_):
             except KeyError:
                 pass
             try:
-                # this will raise if the task was cancelled
                 _ = task.result()
             # pylint: disable=W0718
             except Exception:
                 pass
+            except asyncio.CancelledError:
+                pass
 
         task.add_done_callback(safe_remove)