Test base branch as well when testing on topic failed, and use it as a reference

[famz]

When tests on a new series failed, it may or may not be a flaw in the patch: testing environmental errors, including disk space limitations, unstable network or existing bugs can all cause test failures.

Limit the email report to only when "base" commit passes but the "topic" branch fails, which gives much higher confidence for geniune bugs in the series.