a bunch of fixes for error handling (#19627)

- handle errFileCorrupt properly
- micro-optimization of sending done() response quicker
  to close the goroutine.
- fix logger.Event() usage in a couple of places
- handle the rest of the client to return a different error other than
  lastErr() when the client is closed.

cmd/erasure-metadata.go

@@ -403,7 +403,7 @@ func writeUniqueFileInfo(ctx context.Context, disks []StorageAPI, origbucket, bu
 			if fi.IsValid() {
 				return disks[index].WriteMetadata(ctx, origbucket, bucket, prefix, fi)
 			}
-			return errCorruptedFormat
+			return errFileCorrupt
 		}, index)
 	}