Avoiding unintentional multi run builds when results inserted in parallel

[Muusssi]

Some times when to builds are inserted in parallel without explicit build numbers, the builds may receive the same build number and can be unintentionally be filed under the same build. This tends to be problem especially with the "All builds" series which does not even have any explicit build number.

Proposed mitigation:
Isolate the series mapping in the end as a possibly separate transaction to avoid two in parallel inserted builds receiving the same build number unintentionally.