pack: free idx objects after write
pack: free idx objects after write

Make unmap_write_idx free the objects after writing them to the index.

Signed-off-by: Ramkumar Ramachandra <5c355d1d38066ed0c5de420d67c1b5ed0687c4bd@gmail.com>

artagnon/phoenixfs,artagnon/phoenixfs,artagnon/phoenixfs