Revert "simplify dissconnect logic". The idea with task cancelation doesn't work

This reverts commit a20b1c9929.

mtprotoproxy.py

@@ -795,6 +795,7 @@ async def handle_client(reader_clt, writer_clt):
                 if not data:
                     wr.write_eof()
                     await wr.drain()
+                    wr.close()
                     return
                 else:
                     update_stats(user, octets=len(data))
@@ -803,6 +804,8 @@ async def handle_client(reader_clt, writer_clt):
         except (OSError, asyncio.streams.IncompleteReadError) as e:
             # print_err(e)
             pass
+        finally:
+            wr.transport.abort()
 
     task_tg_to_clt = asyncio.ensure_future(connect_reader_to_writer(reader_tg, writer_clt, user))
     task_clt_to_tg = asyncio.ensure_future(connect_reader_to_writer(reader_clt, writer_tg, user))