Revert commits 220b9d4 and 3698c93

 The fix in commit 3698c93 to prevent crashes intorduced by commit
 220b9d4 ended up triggering a race condition related to collecting the
 exit status or exit signal information on a process. There's stil an
 issue that needs to be addressed when remote systems don't close the
 channel in a timely manner which can cause problems handling something
 like a KeyboardInterrupt, but the attempted fix seemed to be doing more
 harm than good. Until a different approach can be found, the code has
 been reset back to what it was before these two commits.

asyncssh/channel.py

@@ -229,7 +229,7 @@ def _cleanup(self, exc: Optional[Exception] = None) -> None:
 
         self._close_event.set()
 
-        if self._conn and self._recv_state == 'closed': # pragma: no branch
+        if self._conn: # pragma: no branch
             self.logger.info('Channel closed%s',
                              ': ' + str(exc) if exc else '')
 
@@ -263,8 +263,7 @@ def _discard_recv(self) -> None:
         # If recv is close_pending, we know send is already closed
         if self._recv_state == 'close_pending':
             self._recv_state = 'closed'
-
-        self._loop.call_soon(self._cleanup)
+            self._loop.call_soon(self._cleanup)
 
     async def _start_reading(self) -> None:
         """Start processing data on a new connection"""
@@ -413,11 +412,7 @@ def _service_next_request(self) -> None:
         handler = cast(_RequestHandler, getattr(self, name, None))
 
         if handler:
-            if self._session:
-                result = cast(Optional[bool], handler(packet))
-            else:
-                # Ignore requests received after application closes the channel
-                result = True
+            result = cast(Optional[bool], handler(packet))
         else:
             self.logger.debug1('Received unknown channel request: %s', request)
             result = False