Remaining race-condition in the copy UI

There is still a remaining race-condition in the copy UI.

Illegal source-only copies will be erroneously allowed for the in the short time-window after the build(s) have completed successfully and before their binaries gets published.

{{{
>----< source upload (0 min) >-------------< built succesfully >-----Illegal source-only copies-----< binaries published >------->
}}}

A solution could be either check for this situation in the copy UI as we already for for 'bullding source' or 'already published binaries' or we could publish binaries in upload time as we do for sources (actually, we can publish any upload w/o custom files in upload-time).