Move error handling of invalid zvols to when the user clicks 'Next' in VM wizard
When typing the path of new disk image creation, the field is reset if an invalid choice is made. I will start typing /mnt, but when the final t is typed, the field is whiped and a message 'Virtual machines cannot be stored in an unmounted mountpoint: /mnt'. This makes one unable to type '/mnt/pool1', for example. Is it possible to keep what is typed in the form until the user clicks 'Next', whereby the form will be cleared and the error message appears? Either that, or disallow the user to type a path and force selection of paths from the directory view.