prscript: iterate on builds when checking status

prscript: iterate on builds when checking status

This patch is changing the logic when using docker mode. We are
iterating over each builds so we know when one build is over in
the 5 seconds following the event instead of getting the result
when the builds that are checked before are others.

On OISF's build system, the two builds comes out in order so there
is no problem.