Don't clobber msg loop mem chan on rx stream close

Revert this change since it really is poking at internals and doesn't
make a lot of sense. If the context is going to be cancelled then the
msg loop will tear down the feed memory channel when ready, we don't
need to be clobbering it and confusing the runtime machinery lol.

tractor/_portal.py

@@ -332,12 +332,6 @@ class Portal:
             # message right now since there shouldn't be a reason to
             # stop and restart the stream, right?
             try:
-
-                # We are for sure done with this stream and no more
-                # messages are expected to be delivered from the
-                # runtime's msg loop.
-                await recv_chan.aclose()
-
                 await ctx.cancel()
 
             except trio.ClosedResourceError:

tractor/_streaming.py

@@ -61,7 +61,7 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
         return msg['yield']
 
     async def receive(self):
-        # see ``.aclose()`` to an alt to always checking this
+        # see ``.aclose()`` for an alt to always checking this
         if self._eoc:
             raise trio.EndOfChannel
 
@@ -80,7 +80,6 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
 
             if msg.get('stop'):
                 log.debug(f"{self} was stopped at remote end")
-                self._eoc = True
 
                 # when the send is closed we assume the stream has
                 # terminated and signal this local iterator to stop
@@ -150,6 +149,8 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
         on close.
 
         """
+        self._eoc = True
+
         # XXX: keep proper adherance to trio's `.aclose()` semantics:
         # https://trio.readthedocs.io/en/stable/reference-io.html#trio.abc.AsyncResource.aclose
         rx_chan = self._rx_chan
@@ -200,8 +201,6 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
                 # it can't traverse the transport.
                 log.debug(f'Channel for {self} was already closed')
 
-        self._eoc = True
-
         # close the local mem chan??!?
 
         # NOT if we're a ``MsgStream``!