[core] always lseek() with shared fd

always lseek() with shared fd; remove optim to skip with offset = 0

src/chunk.c

@@ -882,7 +882,7 @@ chunkqueue_small_resp_optim (chunkqueue * const restrict cq)
     const int fd = filec->file.fd;
     if (fd < 0) return; /*(require that file already be open)*/
     off_t offset = filec->offset;
-    if (0 != offset && -1 == lseek(fd, offset, SEEK_SET)) return;
+    if (-1 == lseek(fd, offset, SEEK_SET)) return;
 
     /* Note: there should be no size change in chunkqueue,
      * so cq->bytes_in and cq->bytes_out should not be modified */

src/http_chunk.c

@@ -76,7 +76,7 @@ static int http_chunk_append_read_fd_range(request_st * const r, const buffer *
     if (r->resp_send_chunked)
         http_chunk_len_append(cq, (uintmax_t)len);
 
-    if (0 != offset && -1 == lseek(fd, offset, SEEK_SET)) return -1;
+    if (-1 == lseek(fd, offset, SEEK_SET)) return -1;
     buffer * const b = chunkqueue_append_buffer_open_sz(cq, len+2+1);
     ssize_t rd;
     offset = 0;