Issue #1323: Default synced folder type to vagrant_synced_fodler_default_type if unset

Author: oxyc

Vagrantfile

@@ -137,7 +137,7 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
   # Synced folders.
   vconfig['vagrant_synced_folders'].each do |synced_folder|
     options = {
-      type: synced_folder['type'],
+      type: synced_folder.include?('type') ? synced_folder['type'] : vconfig['vagrant_synced_folder_default_type'],
       rsync__auto: 'true',
       rsync__exclude: synced_folder['excluded_paths'],
       rsync__args: ['--verbose', '--archive', '--delete', '-z', '--chmod=ugo=rwX'],