For all socket, set SO_LINGER to reduce delays until socket reuse in case of interrupted TCP connection closes.

In the lwIP accept callback, we should set SO_LINGER scoket option with a reduced linger time, e.g. two seconds. This will allow faster reuse of sockets in certain situations, since we don't have to spend the full 2MSL (120secs) delay waiting for the peer to send remaining data (would not be accepted by the stack anyway).