Bug#984596: debian-edu-config: dhcpd fails to start due to missing leases file
During recent installation media tests I noticed that isc-dhcp-server failed
to start. This happens when switching from the init script to a custom
systemd service file (via cfengine at the end of the installation process).
This switch has been needed because the LDAP connection is broken if the init
script is used (#971275).
As the dhcpd server could not start successfully, the /var/lib/dhcpd.leases
file is missing.
So to really fix #971275 in all possible cases, cf3/cf.dhcpserver should also
care for the leases file.