Add CN shutdown netboot hook

Some platforms has networking dependencies between CN and BMC, thus need
to keep the host down during bmc install.

This is a refactor of https://gbmc-internal-review.git.corp.google.com/c/meta-google-gbmc/+/224106

Tested: hook is correctly installed

Fusion-Link: https://fusion2.corp.google.com/ci/guitar/projects/null/activity/f1d8de65-8af0-4636-9a55-eb0a4c6fc5b1/overview

Google-Bug-Id: 407103562
Change-Id: I26f72d670a9943d74c60f884ee05a055049a12ef
Signed-off-by: yuxiaozhang <yuxiaozhang@google.com>
1 file changed
tree: 4a3f1733cefc47a7d2655191df6132c6d0801a69
  1. linux/
  2. .gitmodules