Set cancelled state in cancel method

tests/test_tractor.py

@@ -247,7 +247,6 @@ async def test_trynamic_trio():
             'gretchen',
             main=partial(say_hello, 'donny'),
             rpc_module_paths=[__name__],
-            # outlive_main=True
         )
         print(await gretchen.result())
         print(await donny.result())
@@ -361,6 +360,7 @@ async def aggregate(seed):
             async for value in await portal.run(
                 __name__, 'stream_data', seed=seed
             ):
+                # leverage trio's built-in backpressure
                 await q.put(value)
 
             await q.put(None)

tractor/__init__.py

@@ -867,6 +867,7 @@ class ActorNursery:
 
         log.debug(f"Waiting on all subactors to complete")
         await self.wait()
+        self.cancelled = True
         log.debug(f"All subactors for {self} have terminated")
 
     async def __aexit__(self, etype, value, tb):
@@ -891,7 +892,6 @@ class ActorNursery:
             except Exception as err:
                 log.warn(f"Nursery caught {err}, cancelling")
                 await self.cancel()
-                self.cancelled = True
                 raise
             log.debug(f"Nursery teardown complete")