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".