DHCP relay doesn't work on boot when a lot of VLAN network interfaces

[EOLE team]

1) lsb_release -rd
Description: Ubuntu 14.04.5 LTS
Release: 14.04

2) apt-cache policy isc-dhcp-relay
isc-dhcp-relay:
  Installé : 4.2.4-7ubuntu12.13
  Candidat : 4.2.4-7ubuntu12.13

We are using isc-dhcp package on Ubuntu trusty server.
The server has 4 physical network interfaces and several VLAN on eth2 interface.
dhcrelay is configured to relay dhcp requests from eth3 to VLAN interfaces.

On boot, depending on hardware velocity, the DHCP relay doesn't work.
In /etc/init/isc-dhcp-relay.conf, we can see "start on runlevel [2345]", but if all network interfaces are not ready, some errors appear in log file :
"2018-03-20T10:58:45.229688+01:00 amon.etb1.lan dhcrelay: Error getting hardware address for "eth2.4": No such device"
We must restart isc-dhcp-relay service once all network interfaces are ready.

To resolve this problem, we added /etc/init/isc-dhcp-relay.override file containing "start on (runlevel [2345] and static-network-up)" to make sure that isc-dhcp-relay starts when all network interfaces are ready.

Can we hope that you integrate this hotfix ?