JENKINS-11655: If many builds trigger same downstream job, wrong artifac...

...ts are copied, first job triggered, not last / newest like would be assumed. In this commit it is fixed.

Because this is a big changes it may be reasonable to have some global configuration checkbox if used newestbuild instead of first build when artifacts are copied. I tried to do it also, but my competence was not enough. Those tries are in comment in this commit.

One possibility is also add selection of copy order to job configuration, but then each job have to configure separately. Al least I like each job acting same like, that why I think global configure is better. 

For me also possibility that copy artifact acts like this allways is okay, but it may cause some problems other as they are planning own jobs so that artifacts are copied from firat build triggered downstream build.