sync: fix logic error with linkfile errors

Make sure err_update_linkfiles is always initalized.

Bug: https://crbug.com/gerrit/11008
Change-Id: I7bdd91f82507608ef967daf0fa0f9c859454e19f
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/305146
Reviewed-by: Raman Tenneti <rtenneti@google.com>
Tested-by: Mike Frysinger <vapier@google.com>