Comment 8 for bug 1447715

This is still an issue in Ubuntu Server 16.04.1. I have the following in my /etc/network/interfaces file:

# The primary network interface
auto ens3
iface ens3 inet dhcp
# This is an autoconfigured IPv6 interface
iface ens3 inet6 auto
    dhcp 1

And on startup:
Aug 5 15:55:23 flounder dhclient[2483]: Can't bind to dhcp address: Cannot assign requested address

Can confirm the "gross ugly hack" in #7 works. I suggest involving the ifupdown and NetworkManager maintainers as well since their tools should probably be aware of the state of the link and can control when dhclient is invoked.