quiet "shard X not found" log when EC shard lives on another server
When EC shards are spread across multiple volume servers, every read
that targets a shard not present locally was logging at V(0) with the
same wording as a real read failure. Under rclone-style traffic this
floods the logs and makes a healthy EC cluster look broken (issue #9310).
Distinguish the two cases with an errShardNotLocal sentinel: the
expected fall-through-to-remote path now logs at V(4); genuine local
read failures still log at V(0).
Chris Lu
57bb7b2f39