Enable scaleway-ipv6 flag

[QuentinPerez]

closes #50

Setup a new machine with --scaleway-ipv6

$ docker-machine create -d scaleway --scaleway-name="scw-docker01" --scaleway-ipv6 --scaleway-commercial-type "VC1S"  scw-docker01
Running pre-create checks...
Creating machine...
(scw-docker01) Creating SSH key...
(scw-docker01) Creating server...
(scw-docker01) Starting server...
Waiting for machine to be running, this may take a few minutes...
Detecting operating system of created instance...
Waiting for SSH to be available...
Detecting the provisioner...
Provisioning with ubuntu(systemd)...
Installing Docker...
Copying certs to the local machine directory...
Copying certs to the remote machine...
Setting Docker configuration on the remote daemon...
Checking connection to Docker...
Docker is up and running!
To see how to connect your Docker Client to the Docker Engine running on this virtual machine, run: docker-machine env scw-docker01

root@ip:~# ping6  2001:bc8:4400:2100::4:417
PING 2001:bc8:4400:2100::4:417(2001:bc8:4400:2100::4:417) 56 data bytes
64 bytes from 2001:bc8:4400:2100::4:417: icmp_seq=1 ttl=59 time=0.609 ms

And it works without any reboot on VC*

[moul]

LGTM