set-datetime: Use timedatectl to force flush the time to disk

Previously if you "rudely" unplugged the board and plugged it back in, it would
revert to 2016 because systemd-timesync didn't write its timestamp to disk.

Change-Id: If5830cb26152381814190dfbd732081a38880992
2 files changed
tree: c3546cc5c87557a266a63f4c676b03005f97b308
  1. debian/
  2. etc/
  3. usr/