nova-objectstore logrotate script uses 'dpkg-vendor'

nova-objectstore's logrotate script uses 'dpkg-vendor' to try determine how to restart nova-objectstore. This requires 'dpkg-dev' to be installed which is not desirable.

The script really should use /etc/lsb-release.

Current logrotate script (/etc/logrotate.d/nova-objectstore):

    /var/log/nova/nova-objectstore.log {
        daily
        missingok
        postrotate
            if dpkg-vendor --derives-from ubuntu ; then
                restart nova-objectstore
            else
                invoke-rc.d nova-objectstore restart 2>&1 >/dev/null
            fi
        endscript
    }

Related bugs:
- LP#781716 Post install check assumes dpkg-vendor

System information:
- DISTRIB_DESCRIPTION="Ubuntu 11.10"
- nova-objectstore 2011.3-0ubuntu6.3