cloud-setup: clear error variable in nmcs_device_reapply()

This is rather bad, because if we reach the "goto again" case,
the error variable is not cleared. Subsequently passing the
error location to nm_device_reapply_finish() will trigger a glib
warning.

Fixes: 29b0420be7 ('nm-cloud-setup: set preserve-external-ip flag during reapply')

src/nm-cloud-setup/nm-cloud-setup-utils.c

@@ -581,6 +581,8 @@ nmcs_device_reapply(NMDevice     *device,
     NMDeviceReapplyFlags reapply_flags = NM_DEVICE_REAPPLY_FLAGS_PRESERVE_EXTERNAL_IP;
 
 again:
+    g_clear_error(&data.error);
+
     nm_device_reapply_async(device,
                             connection,
                             version_id,