unit-tests: Let the TLS server thread close its own socket

Closing the socket from the main thread, while the server thread is
still in accept() (or is just about to enter it), seems to
occasionally cause a deadlock on macOS.

src/libtls/tests/suites/test_socket.c

@@ -493,13 +493,17 @@ START_TEARDOWN(teardown_creds)
 	if (server_config)
 	{
 		shutdown(server_config->fd, SHUT_RDWR);
-		close(server_config->fd);
 		free(server_config);
 		server_config = NULL;
 	}
 }
 END_TEARDOWN
 
+static void close_fd_ptr(void *fd)
+{
+	close(*(int*)fd);
+}
+
 /**
  * Run an echo server
  */
@@ -519,6 +523,7 @@ static job_requeue_t serve_echo(echo_server_config_t *config)
 	}
 	sfd = config->fd;
 	thread_cleanup_push((thread_cleanup_t)server->destroy, server);
+	thread_cleanup_push(close_fd_ptr, &sfd);
 	while (TRUE)
 	{
 		oldstate = thread_cancelability(TRUE);
@@ -554,6 +559,7 @@ static job_requeue_t serve_echo(echo_server_config_t *config)
 		close(cfd);
 	}
 	thread_cleanup_pop(TRUE);
+	thread_cleanup_pop(TRUE);
 
 	return JOB_REQUEUE_NONE;
 }