btrfs: Open-code name_in_log_ref in replay_one_name

That function adds unnecessary indirection between backref_in_log and
the caller. Furthermore it also "downgrades" backref_in_log's return
value to a boolean, when in fact it could very well be an error.

Rectify the situation by simply opencoding name_in_log_ref in
replay_one_name and properly handling possible return codes from
backref_in_log.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update comment ]
Signed-off-by: David Sterba <dsterba@suse.com>