bind: fix leak in ssh_bind_accept error path

Use 'ssh_socket_free' to cleanup if 'ssh_bind_accept_fd'
fails, to be sure to free the ssh_socket in/out buffers.

src/bind.c

@@ -454,8 +454,7 @@ int ssh_bind_accept(ssh_bind sshbind, ssh_session session) {
 #else
       close(fd);
 #endif
-      if (session->socket)
-          ssh_socket_close(session->socket);
+      ssh_socket_free(session->socket);
   }
   return rc;
 }