Fix vagrant up with ubuntu/xenial64

There is the following bug in ubuntu/xenial64 cloud image.
https://bugs.launchpad.net/cloud-images/+bug/1569237
This will cause that vagrant user will not exist.

Change-Id: Iacc4135fa165d8624ad61c4e5170683180234cbf
Closes-Bug: #1687197

contrib/vagrant/Vagrantfile

@@ -30,6 +30,9 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
     v.video_type    = 'qxl'
   end
 
+  config.ssh.username = "ubuntu"
+  config.vm.provision "shell", path: "add_vagrant_user.sh"
+
   config.vm.synced_folder '../../devstack/', '/devstack'
   # For CentOS machines it needs to be specified
   config.vm.synced_folder '.', '/vagrant'

contrib/vagrant/add_vagrant_user.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+echo "create user vagrant"
+adduser --disabled-password --gecos "" vagrant
+echo 'vagrant:vagrant' | chpasswd
+ls -al /home/
+echo "add sudo privilege to user vagrant"
+cp /etc/sudoers.d/90-cloud-init-users /etc/sudoers.d/admin
+chmod +w /etc/sudoers.d/admin
+ls -al /etc/sudoers.d/
+sed -i 's/ubuntu/vagrant/g' /etc/sudoers.d/admin
+cat /etc/sudoers.d/admin
+echo "enable ssh access for user vagrant"
+mkdir /home/vagrant/.ssh
+cat /home/ubuntu/.ssh/authorized_keys > /home/vagrant/.ssh/authorized_keys
+chown vagrant:vagrant -R /home/vagrant/.ssh
+su - vagrant -c "cat /home/vagrant/.ssh/authorized_keys"
+chmod 600 /home/vagrant/.ssh/authorized_keys
+ls -al /home/vagrant/.ssh
+chmod 700 /home/vagrant/.ssh
+ls -al /home/vagrant