osd: transaction get_encoded_bytes() now consider whether use tbl

When use_tbl is true get_encoded_bytes() has the same logic as before,
when use_tbl is false, it has to calculate the encoded bytes.

Change-Id: I9e1827cb866e1e64d7c6a414482d28f91b5b6aff
Signed-off-by: Dong Yuan <yuandong1222@gmail.com>
Temp

Change-Id: I24512fa50e2aaf71caff057b2e2378229927bc48
Signed-off-by: Dong Yuan <yuandong1222@gmail.com>