Minijack: Fix bug that minijack --help returning an error

Running Minijack with the --help option failed because the attribute
_file_scanner is not initialized. This change fixes this issue.

BUG=None
TEST=Manual
Run 'minijack --help' without any error.

Change-Id: I040cddffeda1afd6c646434a50c3483e5cbbae89
Reviewed-on: https://chromium-review.googlesource.com/169733
Reviewed-by: Dean Liao <deanliao@chromium.org>
Commit-Queue: Wai-Hong Tam <waihong@chromium.org>
Tested-by: Wai-Hong Tam <waihong@chromium.org>
1 file changed