git-codereview: fix loadAuth bug from CL 1771

I have a test for this code now. The test found this.
The test will be sent in a different, non-TBR CL.

Change-Id: I98f5bc22577d7aded284ab9d1bf4fe68b10c2b87
Reviewed-on: https://go-review.googlesource.com/2112
Reviewed-by: Russ Cox <rsc@golang.org>