require_hint_crc value is ignored

[evanmcc]

https://github.com/basho/bitcask/blob/1.6/src/bitcask_fileops.erl#L477 should return Acc, not <<>>. The empty binary looks sensible but it actually breaks the fold. This essentially forces require_hint_crc to true even though it defaults to false.

To fix this we need to change the line to return Acc, change the bulk crc check to not happen if require_hint_crc is false, and also to maintain safety, we should default require_hint_crc to true.

[slfritchie]

Closing: fixed in develop at/earlier than this:

bitcask/src/bitcask_fileops.erl

Line 604 in f40fb00

{done, Acc}