So the slaves have docker-engine

$ apt-cache policy docker-engine
docker-engine:
  Installed: 1.12.6-0~debian-jessie
  Candidate: 1.12.6-0~debian-jessie
  Version table:
 *** 1.12.6-0~debian-jessie 0
       1001 http://apt.wikimedia.org/wikimedia/ jessie-wikimedia/thirdparty amd64 Packages
        100 /var/lib/dpkg/status

That apparently comes from profile::ci::docker.

To upgrade we would want to switch to:

apt::repository { 'thirdparty-ci':
    uri        => 'http://apt.wikimedia.org/wikimedia',
    dist       => "${::lsbdistcodename}-wikimedia",
    components => 'thirdparty/ci',
}
package { 'docker-ce':
    ensure => present,
}

Change 379556 had a related patch set uploaded (by Hashar; owner: Hashar):
[operations/puppet@production] contint: docker-ce on labs docker slaves

https://gerrit.wikimedia.org/r/379556

Mentioned in SAL (#wikimedia-releng) [2017-09-22T08:44:32Z] <hashar> Upgraded docker on integration-slave-docker-1001 and integration-slave-docker-1002 - T176267

Change 379726 had a related patch set uploaded (by Hashar; owner: Hashar):
[operations/puppet@production] Decouple profile::ci::docker and arcanist install

https://gerrit.wikimedia.org/r/379726

Change 379727 had a related patch set uploaded (by Hashar; owner: Hashar):
[operations/puppet@production] Decouple profile::ci::docker and zuul-cloner install

https://gerrit.wikimedia.org/r/379727

Change 379728 had a related patch set uploaded (by Hashar; owner: Hashar):
[operations/puppet@production] Decouple profile::ci::docker and worker_localhost

https://gerrit.wikimedia.org/r/379728

Change 379726 merged by Alexandros Kosiaris:
[operations/puppet@production] Decouple profile::ci::docker and arcanist install

https://gerrit.wikimedia.org/r/379726

Change 379727 merged by Alexandros Kosiaris:
[operations/puppet@production] Decouple profile::ci::docker and zuul-cloner install

https://gerrit.wikimedia.org/r/379727

Change 379728 merged by Alexandros Kosiaris:
[operations/puppet@production] Decouple profile::ci::docker and worker_localhost

https://gerrit.wikimedia.org/r/379728

Change 379556 merged by Alexandros Kosiaris:
[operations/puppet@production] contint: docker-ce on labs docker slaves

https://gerrit.wikimedia.org/r/379556