LU-700 osc: Tally BRW_{READ,WRITE}_BYTES by bytes transferred.

LU-700 osc: Tally BRW_{READ,WRITE}_BYTES by bytes transferred.

Call ptlrpc_lprocfs_brw() in brw_interpret() rather than
osc_send_oap_rpc() and tally by the number of bytes transferred rather
than the number requested.

Change-Id: Ia7191972d9671f01d942a46eba069191f130f516
Signed-off-by: John L. Hammond <jhammond@tacc.utexas.edu>
Reviewed-on: http://review.whamcloud.com/1402
Tested-by: Hudson
Reviewed-by: Jinshan Xiong <jay@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>