Fix info file naming upon import

Current behaviour: Upon import, schnapps prepends a @ to the info file's name, e.g., @19.info (@19 is the subvolume's name). This makes it 'invisible' to schnapps, e.g., schnapps list.

Expected behaviour: A file name of 19.info.

This issue was reported in the forum. Patch !15 (closed) should rectify it.