Bug 1077136 - new async task to catch missing resultsets

ready for merge

@maurodoglio - would you do the honors?  :)
An alternative to that would be to compute a set difference between the revisions found in the buildapi file and the revisions we have a lookup for. If we do it just after we get the lookup, we could loop on the known revisions only, saving quite a bit of time I guess. We can chat about it and eventually implement it as a second step if we need to improve the performances of the job ingestion