chroot: use systemd-timesyncd.service by defualt if avaiable

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
chroot: report systemd-timesyncd

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
bb.org: key expired on debian.beagleboard.org repos.rcn-ee.net is setup to replace, so drop bb.org repo

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>