[JENKINS-17751] added tests for a combination with Promoted Builds plugin.
[FIX JENKINS-17751] Called from a promotion, set UpstreamCause from the original build of the promotion.
[JENKINS-17751] removed unnecessary `super`. It is misleading.
Merge pull request #40 from ikedam/feature/JENKINS-17751-2

[JENKINS-17751] set upstream builds to original builds of promotions(improvement of #38)