autoupdate: select correct x_forwarded_host

If the X-Forwarded-Host header field has multiple values, current code
is not selecting the correct value. Update GetDevserverUrl() so that the
right most host is selected.

BUG=chromium:1082085
TEST=Manually tested on chromeos2-devservertest

Change-Id: I194574a2cccb8295b72d4dbb80401c785e6c5e60
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2216809
Tested-by: Sanika Kulkarni <sanikak@chromium.org>
Reviewed-by: Congbin Guo <guocb@chromium.org>
Commit-Queue: Congbin Guo <guocb@chromium.org>
Auto-Submit: Sanika Kulkarni <sanikak@chromium.org>
1 file changed