We have to use refs/remotes/origin/foo instead of refs/heads/foo,
as refs/heads/foo might not be defined.

https://logs.chromium.org/logs/infra-internal/buildbucket/cr-buildbucket.appspot.com/8853851694141987488/+/u/build/git_cl_upload/stdout

Change-Id: Ic729510d7beca63c25ea84394758cb62f76c572f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2729615
Auto-Submit: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>