build_inf.sh: lockdown layers on specific commits

build_inf.sh: lockdown layers on specific commits

Lockdown all the Yocto layers/repos on specific commits to avoid
potential issues in the future when changes happen in upstream
Yocto layers/repos, the change includes:

- Remove the -s option so it will never try to update the repo
- Add specific commit for each yocto layer/repo
- Improve the clone_update_repo function so it will checkout
  to specific commit after clone.

Issue-ID: INF-154
Signed-off-by: Jackie Huang <jackie.huang@windriver.com>
Change-Id: I7e66680d71bea3ebace07a36b77fb009788c3494