The binary that it's trying to call when starting the process is dhcrelay3 but it's now named dhcrelay.

Looking into the git, there is 3 hits to change :

scripts/system/dhcrelay.init: OUTPUT=start-stop-daemon -m --pidfile $PIDFILE -b --start --exec /usr/sbin/dhcrelay3 -- -d $ARGS 2>&1
scripts/system/dhcv6relay-status.pl:my $ps_output=ps -C dhcrelay3 -o args --no-headers;
scripts/system/dhcv6relay.init: OUTPUT=start-stop-daemon -m --pidfile $PIDFILE -b --start --exec /usr/sbin/dhcrelay3 -- -d -6 $ARGS 2>&1