update default vagrant box to ubuntu 15

Vagrantfile

@@ -18,8 +18,8 @@ pkgs = %w(
 
 Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
 
-  config.vm.box = "ubuntu/ubuntu-14.10-amd64"
-  config.vm.box_url = "https://cloud-images.ubuntu.com/vagrant/utopic/current/utopic-server-cloudimg-amd64-vagrant-disk1.box"
+  config.vm.box = "ubuntu/ubuntu-15.04-amd64"
+  config.vm.box_url = "https://cloud-images.ubuntu.com/vagrant/vivid/current/vivid-server-cloudimg-amd64-vagrant-disk1.box"
 
   config.vm.network "private_network", ip: vm_ip
   config.vm.provider :virtualbox do |vb|

vagrant-common.rb

@@ -45,9 +45,10 @@ end
 def tweak_docker_daemon(vm)
   vm.provision :shell, :inline => <<SCRIPT
 usermod -a -G docker vagrant
-echo 'DOCKER_OPTS="-H unix:///var/run/docker.sock -H tcp://0.0.0.0:2375"' \
-  >> /etc/default/docker
-service docker restart
+sed -i -e's%-H fd://%-H fd:// -H tcp://0.0.0.0:2375 -s overlay%' /lib/systemd/system/docker.service
+systemctl daemon-reload
+systemctl start docker
+systemctl enable docker
 SCRIPT
 end