Should we use the Yocto stable branch for testing?

[pbrkr]

Currently we're building from the Yocto Project master branch when testing pull requests. The benefits of this is that we're not surprised by upstream changes when the next release comes out, instead we follow the changes as they happen. The possible drawback is that master can be unstable at times and we don't want potential contributors to see their merge request fail the automated tests due to upstream changes.