doReadRemoteEcShardInterval accepted an immediate EOF or a short stream and
returned success with a partly zero-filled, unvalidated buffer (the server
stamps the identity only on chunks that carry bytes). A non-deleted interval
must arrive whole: require n == len(buf), exempting the is_deleted
short-circuit (n=0), matching readLocalEcShardInterval's local check. A short
read now fails so the caller recovers from parity.
Chris Lu
a2a8f56c41