check-upstart-scripts: Fix for shellcheck SC2295

Quote $D so it doesn't try to get matched as a pattern. Not sure if that
can ever happen in practice with e.g. `../` in paths.

BUG=None
TEST=CQ only

Change-Id: Icdccbf3a8dfb0d05c8503a525035806b980fd350
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/4861163
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Andrew Moylan <amoylan@chromium.org>
Tested-by: Andrew Moylan <amoylan@chromium.org>
1 file changed