Vagrantfile: rsync symlinks as symlinks, fixes #592

Vagrantfile

@@ -273,7 +273,7 @@ end
 
 Vagrant.configure(2) do |config|
   # use rsync to copy content to the folder
-  config.vm.synced_folder ".", "/vagrant/borg/borg", :type => "rsync"
+  config.vm.synced_folder ".", "/vagrant/borg/borg", :type => "rsync", :rsync__args => ["--verbose", "--archive", "--delete", "-z"]
   # do not let the VM access . on the host machine via the default shared folder!
   config.vm.synced_folder ".", "/vagrant", disabled: true