Go back to using docker exec in cloudron exec

The main issue is that multiple cloudron exec sessions do not
share the same rootfs. Which makes it annoying to debug.

We also have some nginx timeout which drops you out of exec
now and then resulting in loss of all state.

src/routes/apps.js

@@ -369,8 +369,5 @@ function exec(req, res, next) {
 
         duplexStream.pipe(res.socket);
         res.socket.pipe(duplexStream);
-
-        res.on('close', duplexStream.close);
     });
 }
-