use hashicorp's wily64 images instead of ubuntu's

The latter suffer from https://github.com/mitchellh/vagrant/issues/6653

Vagrantfile

@@ -18,8 +18,7 @@ pkgs = %w(
 
 Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
 
-  config.vm.box = "ubuntu/ubuntu-15.10-amd64"
-  config.vm.box_url = "https://cloud-images.ubuntu.com/vagrant/wily/current/wily-server-cloudimg-amd64-vagrant-disk1.box"
+  config.vm.box = "ubuntu/wily64"
 
   config.vm.network "private_network", ip: vm_ip
   config.vm.provider :virtualbox do |vb|

test/Vagrantfile

@@ -14,8 +14,7 @@ require '../vagrant-common.rb'
 def configure_docker(host, hostname, ip)
   pkgs = %w(docker-engine ethtool)
 
-  host.vm.box = "ubuntu/ubuntu-15.10-amd64"
-  host.vm.box_url = "https://cloud-images.ubuntu.com/vagrant/wily/current/wily-server-cloudimg-amd64-vagrant-disk1.box"
+  host.vm.box = "ubuntu/wily64"
 
   host.vm.provision :shell, :inline => "hostnamectl set-hostname "+hostname
   host.vm.network "private_network", ip: ip