don't create Koji Build object, let OSBS create it using Content Generator API

[twaugh]

Currently, the koji-containerbuild 'buildContainer' task creates a Koji Build object, and the 'createContainer' task starts the OSBS build.

Instead, the Build Object should be created by OSBS. In this new scheme, koji-containerbuild does not need to create a Koji Build object at all.

It will still need to stream build logs from the OSBS build, and cancel it when the Koji Task is cancelled.

I'm not clear enough on the difference between buildContainer and createContainer to say whether both are still needed. I tend towards thinking that they are, for multi-arch support(?).

This change is part of the new scheme for Koji integration, in which the Koji Build object is always created by CG import from atomic-reactor.

CC @maxamillion

See also

• koji_promote: always run when configured atomic-reactor#435
• Always configure koji_promote when koji configured osbs-client#366