message: rafs: lower alloc bio desc log level to trace
  Starting a container will result in 5000+ "alloc bio desc offset" logs
  when debug is enabled, which floods log and makes debug harder to do.
diff: @@ -647,7 +647,7 @@ pub trait RafsInode {
  self.has_hole(),
  );
  - debug!(
  + trace!(
  "alloc bio desc offset {} size {} i_size {} blksize {} index_start {} index_end {} i_child_count {}",
  offset, size, self.size(), blksize, index_start, index_end, self.get_child_count()
  );
  