[COOK-3449] Prevent torrent status of checking from prematurely ending blocking downloads

http://tickets.opscode.com/browse/COOK-3449

I ran into issues in this cookbook where the torrent_file provider, when performing a blocking download, would catch a new torrent in the checking state and interpret that to mean the torrent had completed when it really hadn't even begun.

I've updated the torrent_file provider to continue blocking while the torrent is downloading or checking. After this change, I haven't had any further premature exits and blocking downloads are working as advertised.