LU-753 obd: remove obsolete commit callback code

LU-753 obd: remove obsolete commit callback code

Remove old obd_transno_commit_cb() function, which was replaced
by lut_cb_last_committed() in the new LU stack implementation.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Mikhail Pershin <tappro@whamcloud.com>
Change-Id: I789687c63761c2532c02f5a1b827d8625b770c1c
Reviewed-on: http://review.whamcloud.com/4211
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>