UpgradeStatus only checks for ubuntu-release-upgrader upgrades

In add_release_info of the generic ubuntu apport hook we can see the following:

    log = '/var/log/dist-upgrade/main.log'
    if os.path.exists(log):
        mtime = os.stat(log).st_mtime
        human_mtime = time.strftime('%Y-%m-%d', time.gmtime(mtime))
        delta = time.time() - mtime

        # Would be nice if this also showed which release was originally installed
        report['UpgradeStatus'] = 'Upgraded to %s on %s (%d days ago)' % (release_codename, human_mtime, delta / 86400)
    else:
        report['UpgradeStatus'] = 'No upgrade log present (probably fresh install)'

UpgradeStatus doesn't take into consideration the possibility that people upgraded by editing their sources.list file and ran 'apt-get dist-upgrade', so saying it is "probably a fresh install" is wrong. Apport can up creating reports with a InstallationMedia of Precise, DistroRelease of Yakkety, but then a UpgradeStatus of "No upgrade log present..." which is wrong.