osd: log inconsistent shard sizes

osd: log inconsistent shard sizes

When an OSD asserts because it cannot recover from an unexpected erasure
coded shard size, the object needs to be manually fixed (i.e. the shard
must be removed so it can be reconstructed). Unfortunately the assert
does not display the name of the object and it is not displayed unless
the OSD logs are >= 10, which is uncommon on an actual cluster because
it creates log files that are too big.

The problem has been fixed in infernalis as part of
https://github.com/ceph/ceph/pull/5173 and backporting it is non
trivial.

The error condition is modified to make it easy for the system
administrator to identify which object is causing the crash and what
steps must be taken to fix the issue.

http://tracker.ceph.com/issues/14009 Refs: #14009

Signed-off-by: Loic Dachary <loic@dachary.org>