Kernel: Remove socket from the listener's accept list when it is closed

Without this patch we end up with sockets in the listener's accept
queue with state 'closed' when doing stealth SYN scans:

Client -> Server: SYN for port 22
Server -> Client: SYN/ACK
Client -> Server: RST (i.e. don't complete the TCP handshake)

Kernel/Net/TCPSocket.cpp

@@ -40,6 +40,9 @@ void TCPSocket::set_state(State new_state)
  if (new_state == State::Closed) {
  Locker locker(closing_sockets().lock());
  closing_sockets().resource().remove(tuple());
+
+ if (m_originator)
+ release_to_originator();
  }
 
  if (previous_role != m_role || was_disconnected != protocol_is_disconnected())
@@ -114,6 +117,7 @@ void TCPSocket::release_to_originator()
 {
  VERIFY(!!m_originator);
  m_originator.strong_ref()->release_for_accept(this);
+ m_originator.clear();
 }
 
 void TCPSocket::release_for_accept(RefPtr<TCPSocket> socket)