Prevent duplicate triggers for the same generated artifacts.

A pipeline trigger for upstream dependency com.example:my-jar:jar:0.7-SNAPSHOT(0.7-20181011.082356-104) should not be triggered several times for this same dependency. Instead, we should update the first build that was caused by "com.example:my-jar:jar:0.7-SNAPSHOT(0.7-20181011.082356-104)" to track the second cause.