odhcpd: remove the "pd_manager" and "pd_cer" options

odhcpd: remove the "pd_manager" and "pd_cer" options

As noted in the previous commit, Homenet is defunct.

The only users of these two options are Homenet/hnetd, so remove the options,
which results in a nice cleanup to src/dhcpv6-ia.c.

We also need to update the Makefile in the main OpenWrt repo.

Signed-off-by: David Härdeman <[email protected]>
Link: https://github.com/openwrt/odhcpd/pull/294
Signed-off-by: Álvaro Fernández Rojas <[email protected]>