stop accidentally downloading some pieces multiple times

[rf]

07:21 PM  rfranknj @ java  ~/code/it/src  ⏎ 130  rarest-piece-first? 
$ grep already bitster.log 
19:17:41 The block 0 was already downloaded
19:17:41 The block 0 was already downloaded
19:17:41 The block 0 was already downloaded
19:17:42 The block 1 was already downloaded
19:17:46 The block 4 was already downloaded
19:17:46 The block 5 was already downloaded
19:17:48 The block 6 was already downloaded
19:17:52 The block 7 was already downloaded
19:18:03 The block 0 was already downloaded
19:18:08 The block 0 was already downloaded
19:18:18 The block 0 was already downloaded
19:18:21 The block 1 was already downloaded
19:18:21 The block 2 was already downloaded
19:18:22 The block 3 was already downloaded
19:18:24 The block 3 was already downloaded
19:18:25 The block 4 was already downloaded
19:18:25 The block 6 was already downloaded
19:18:26 The block 7 was already downloaded
19:18:27 The block 8 was already downloaded
19:18:31 The block 9 was already downloaded
19:18:33 The block 4 was already downloaded
19:18:35 The block 5 was already downloaded
19:18:36 The block 6 was already downloaded
19:18:36 The block 7 was already downloaded
19:18:38 The block 8 was already downloaded
19:18:39 The block 9 was already downloaded
19:18:45 The block 4 was already downloaded
19:18:46 The block 5 was already downloaded
19:19:09 The block 0 was already downloaded
19:19:09 The block 0 was already downloaded
19:19:17 The block 0 was already downloaded
19:19:19 The block 1 was already downloaded
19:19:21 The block 2 was already downloaded
19:19:48 The block 0 was already downloaded
19:19:58 The block 0 was already downloaded
19:20:12 The block 0 was already downloaded
19:20:20 The block 0 was already downloaded

wtf