Change deprecated vagrant ansible flag 'sudo' to 'become'

Vagrantfile

@@ -140,7 +140,7 @@ Vagrant.configure("2") do |config|
           if File.exist?(File.join(File.dirname($inventory), "hosts"))
             ansible.inventory_path = $inventory
           end
-          ansible.sudo = true
+          ansible.become = true
           ansible.limit = "all"
           ansible.host_key_checking = false
           ansible.raw_arguments = ["--forks=#{$num_instances}", "--flush-cache"]