message: rafs: lower down log level when print blob table size
  Otherwise it prints when inspect rafs image/bootstrap
diff: @@ -608,7 +608,7 @@ impl OndiskBlobTable {
  let begin_ptr = data.as_slice().as_ptr() as *const u8;
  let mut frame = begin_ptr;
  - info!("blob table size {}", blob_table_size);
  + debug!("blob table size {}", blob_table_size);
  loop {
  // Each entry frame looks like:
  // u32 | u32 | string | trailing '\0' , except that the last entry has no trailing '\0'
  