package_ipk.bbclass: add lists_dir to sysroots' /etc/opkg.conf

package_ipk.bbclass: add lists_dir to sysroots' /etc/opkg.conf

This makes the sysroots' /etc/opkg.conf agree with opkg-collateral on where
the package lists database should be found. Fixes a problem whereby opkg
cannot find the package lists after opkg-collateral is installed.

This fixes the same problem as acc720fa80227d08fd15764117e0c34e2387e804.
But since that doesn't take into account other dependencies bringing
opkg-collateral into the image, it doesn't solve the problem in all
cases and could probably be reverted.

This is a bit messy, having hardcoded /var/lib/opkg as the lists_dir
in multiple locations. Other suggestions welcome.
I'm not sure its all that necessary to be using /usr/lib/opkg other
than for backwards compatibility with existing installations.

Signed-off-by: Graham Gower <graham.gower@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>