Ensure only Major and Minor version numbers are used for filter.

If a "29.0.1" is released, and product details were updated, and bart were
restarted, it would look for that full version in the logs. This would likely
miss a lot of log lines as downloads of 29.0 would likely continue. This
should fix that so that it continues to only look for "firefox-29.0" followed
by anything but "b".

@jgmize r?