Pass $ST2_RELEASE to docker-compose from CI

[arm4b]

Add ability to pass revision number aka release number from CI, to control package versioning.

st2api_0.14dev-20_amd64.deb

So the version number 0.14dev is parsed from st2common automatically and revision number 20 is injected from outside via ENV.

Same as we have for mistral in docker-compose.

docker-compose should pick up env via docker/compose#1765 when using:

export ST2_RELEASE=20
docker-compose up debian

---

^^ I'm happy that feature with ENV variables was introduced in docker-compose and released in 1.5 version just hours ago. We're lucky here 🍀

Docs: https://github.com/docker/compose/blob/8cc8e61/docs/compose-file.md#variable-substitution

[dennybaa]

👍

[arm4b]

Worked flawlessly in

https://github.com/armab/st2/blob/5736f16a58dbfdc9b30eafb5dc0b959c98f096a9/circle.yml#L51
https://github.com/armab/st2/blob/5736f16a58dbfdc9b30eafb5dc0b959c98f096a9/compose-suite.yml#L14,L15

Thanks Docker 👍