Enable home directory sharing for AFP
Move AFP CNID back to the share directory.

In netatalk 2.x the CNID was contained in the share directory itself.
In netatalk 3.0 this moved to /var/netatalk.

This is a problem on FreeNAS with a large share and it's small /var
After updating netatalk to 3.1.0 a boolean was added that restores
the Netatalk 2.x behavior of storing the CNID in the share.