cache: do not evict entry on ErrClosedPipe (#8432)

Fixes: #8431. If client prematurely closes the read end of the pipe,
cache entry should not be evicted.

cmd/disk-cache-backend.go

@@ -583,9 +583,10 @@ func (c *diskCache) bitrotReadFromCache(ctx context.Context, filePath string, of
 		if _, err := io.Copy(writer, bytes.NewReader((*bufp)[blockOffset:blockOffset+blockLength])); err != nil {
 			if err != io.ErrClosedPipe {
 				logger.LogIf(ctx, err)
-			}
 				return err
 			}
+			eof = true
+		}
 		if eof {
 			break
 		}