mod_image_for_recovery: don't build kernel when --kernel_image specified

If --kernel_image is specified, the script still creates a kernel image
and doesn't use it at all. Move the build kernel step under if clause
to save a few minutes.

Also fixed some lint error

BUG=None
TEST=Run the script manually

Change-Id: Ia73c10cb1166e55d252af7c0dc5f048a349f0d59
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/2294782
Tested-by: Ting Shen <phoenixshen@chromium.org>
Commit-Queue: Ting Shen <phoenixshen@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed