dm flakey: error READ bios during the down_interval
When the corrupt_bio_byte feature was introduced it caused READ bios to
no longer be errored with -EIO during the down_interval. This had to do
with the complexity of needing to submit READs if the corrupt_bio_byte
feature was used.
Fix it so READ bios are properly errored with -EIO; doing so early in
flakey_map() as long as there isn't a match for the corrupt_bio_byte
feature.