Reset the default SSH user to being vagrant.

Using "vagrant ssh" is confusing otherwise.

live-build/ubuntu-cpc/hooks/042-vagrant.binary

@@ -167,8 +167,8 @@ load include_vagrantfile if File.exist?(include_vagrantfile)
 ## We also have an "ubuntu" user with pass "${ubuntu_user_pass}"
 Vagrant.configure("2") do |config|
   config.vm.base_mac = "${macaddr}"
-  config.ssh.username = "ubuntu"
+  config.ssh.username = "vagrant"
-  config.ssh.password = "${ubuntu_user_pass}"
+  config.ssh.password = "vagrant"
 
   config.vm.provider "virtualbox" do |vb|
      vb.customize [ "modifyvm", :id, "--uart1", "0x3F8", "4" ]