qemu-nbd: Fix a memleak in qemu_nbd_client_list()

When the qio_channel_socket_connect_sync() fails
we should goto 'out' label to free the 'sioc' instead of return.

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Alex Chen <alex.chen@huawei.com>
Message-Id: <20201130123651.17543-1-alex.chen@huawei.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

qemu-nbd.c

@@ -181,7 +181,7 @@ static int qemu_nbd_client_list(SocketAddress *saddr, QCryptoTLSCreds *tls,
     sioc = qio_channel_socket_new();
     if (qio_channel_socket_connect_sync(sioc, saddr, &err) < 0) {
         error_report_err(err);
-        return EXIT_FAILURE;
+        goto out;
     }
     rc = nbd_receive_export_list(QIO_CHANNEL(sioc), tls, hostname, &list,
                                  &err);