[FIXED JENKINS-14656] Pass UpstreamCause as well as MyUserIdCause in a single CauseAction

[JENKINS-14656](https://issues.jenkins-ci.org/browse/JENKINS-14656): e.g. Copy Artifact’s plugin’s `TriggeredBuildSelector` calls `Run.getCauses` which only looks for a single `CauseAction`. Need to put all the `Cause`s into this one.