Currently, if a DEPS file sets use_relative_paths, but *also* sets
recursedeps, then the recursed-upon DEPS files still get checked
out relative to the .gclient root. This change makes it so that
recursed-upon DEPS files check their dependencies out relative to
where their parent wants them to be, if that parent sets
use_relative_paths=True.

R=maruel@chromium.org

Review-Url: https://codereview.chromium.org/2324513003