Update Vagrantfile to xenial

boxcutter/ubuntu1604 needs recent Vagrant, so pin at least 1.8.7

Xenial doesn't have Python 2 that ansible needs, so use ansible-bootstrap.sh to get it, though that might be way more than we need.

vagrant/base/devstack/Vagrantfile

-Vagrant.require_version ">= 1.5.3"
+Vagrant.require_version ">= 1.8.7"
 unless Vagrant.has_plugin?("vagrant-vbguest")
   raise "Please install the vagrant-vbguest plugin by running `vagrant plugin install vagrant-vbguest`"
 end
@@ -31,9 +31,8 @@ VERSION_VARS = [
 
 Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
 
-  # Creates a devstack from a base Ubuntu 12.04 image for virtualbox
-  config.vm.box     = "precise64"
-  config.vm.box_url = "http://files.vagrantup.com/precise64.box"
+  # Creates a devstack from a base Ubuntu 16.04 image for virtualbox
+  config.vm.box = "boxcutter/ubuntu1604"
 
   config.vm.network :private_network, ip: vm_guest_ip
 
@@ -72,11 +71,13 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
     vb.customize ["modifyvm", :id, "--natdnshostresolver1", "on"]
   end
 
-
   # Make LC_ALL default to en_US.UTF-8 instead of en_US.
   # See: https://github.com/mitchellh/vagrant/issues/1188
   config.vm.provision "shell", inline: 'echo \'LC_ALL="en_US.UTF-8"\' > /etc/default/locale'
 
+  # Get ready for ansible on this box.
+  config.vm.provision "shell", path: '../../../util/install/ansible-bootstrap.sh'
+
   # Use vagrant-vbguest plugin to make sure Guest Additions are in sync
   config.vbguest.auto_reboot = true
   config.vbguest.auto_update = true