arg: Preserve transfer when freeing out arrays
In case we got an array as out argument we always tried to free the array content even on transfer container.
Fix this by considering the transfer of out arrays, so that:
- Release only the array on transfer container
- Release the array and its content on transfer full
- Do nothing on transfer none (it was already handled)
Fixes a crash that we had with gnome-characters due to the usage of strv with content transfer.