Update docker to 17.03

[tuxity]

There is no major changes, only bugfix. We will be up to date with new docker version system.

https://github.com/docker/docker/releases/tag/v17.03.0-ce

[donny-dont]

Do we have any idea what the versioning will be with Docker going forward? I'm not sure if it should just be 17-dind or explicitly 17.03-dind

[tuxity]

@donny-dont they said :

Starting with this release, Docker is on a monthly release cycle and uses a
new YY.MM versioning scheme to reflect this. Two channels are available: monthly and quarterly.
Any given monthly release will only receive security and bugfixes until the next monthly
release is available. Quarterly releases receive security and bugfixes for 4 months after
initial release. 

[bradrydzewski]

I'm fine with this, but first we need to implement #116 and we need to store the version in a VERSION file. This way if we expect frequent version bumps we don't need to keep re-signing the yaml

[tuxity]

Closing in favor of #122