osd: deep scrub must not abort if hinfo is missing

Instead it should set read_error.

http://tracker.ceph.com/issues/10018 Fixes: #10018

Signed-off-by: Loic Dachary <loic-201408@dachary.org>
(cherry picked from commit 9d84d2e8309d26e39ca849a75166d2d7f2dec9ea)