portage-stable: Import chrony from upstream

Intention is to ship chrony as part of termina rootfs

BUG=chromium:949755
TEST=USE=-caps emerge-tatl chrony

Change-Id: I53ce284a011d3f74c01216e54ed2b4664c2f5ac0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/3404675
Reviewed-by: Anton Romanov <romanton@google.com>
Auto-Submit: Anton Romanov <romanton@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Anton Romanov <romanton@google.com>
Tested-by: Anton Romanov <romanton@google.com>