Speed up vm creation

tests/vagrant/vanilla/Vagrantfile

@@ -7,7 +7,12 @@ Vagrant.configure("2") do |config|
   # vanilla install
 
   config.vm.define "vanilla" do |m1|
-    m1.vm.box = "ubuntu/bionic64"
+    if File.file?("../preloaded/preloaded-ubuntu-bionic64.box")
+      m1.vm.box = "preloaded-ubuntu-bionic64"
+      m1.vm.box_url = "file://" + Dir.pwd + "/../preloaded/preloaded-ubuntu-bionic64.box"
+    else
+      m1.vm.box = "ubuntu/bionic64"
+    end
     m1.vm.network "forwarded_port", guest:443, host:8443, protocol:"tcp"
     m1.vm.provision :shell, :inline => <<-SH
 source globals.sh || exit 1