Clear stale shadow-utils lockfiles before building

If a build is killed in the middle, stale lockfiles for group and user
dbs might get left around. Clean them up in build_packages, build_image,
and update_chroot.

TEST=build_packages with a stale /etc/passwd.lock sitting around.

Change-Id: Ie9887b6b38ba92cc8c008ea15a2f44a0f312b758
Tested-by: Chris Masone <>
Reviewed-by: Mike Frysinger <>
Commit-Queue: Chris Masone <>
4 files changed