docker: update to official 1.3.2 release

This differs from the version on 509.1.0 and 494.1.0 since it is from
the upstream tag instead of a manually applied patch series. The code
and resulting build is identical though.
Merge pull request #969 from marineam/docker

docker: update to official 1.3.2 release
net-misc/ntp: use the coreos ntp vendor pool
sys-apps/systemd: use the coreos ntp vendor pool