Disable audio device mapping for VirtualBox VMs (#6811)

I can't see any reason why audio devices would be needed, and it can cause issues with the host audio

Vagrantfile

@@ -142,6 +142,7 @@ Vagrant.configure("2") do |config|
         vb.gui = $vm_gui
         vb.linked_clone = true
         vb.customize ["modifyvm", :id, "--vram", "8"] # ubuntu defaults to 256 MB which is a waste of precious RAM
+        vb.customize ["modifyvm", :id, "--audio", "none"]
       end
 
       node.vm.provider :libvirt do |lv|