LU-333: Make read_bytes in llite/*/stats report bytes read.

LU-333: Make read_bytes in llite/*/stats report bytes read.

Move ll_stats_ops_tally(..., LPROC_LL_{READ,WRITE}_BYTES, ...) from
vvp_io_init() to the end of ll_file_io_generic(), and tally by the
actual number of bytes read rather than the number requested.

Test 127b, client stats are correctly tallied with this patch.

Change-Id: Icad0bc09630b8c1775f2ec59326902aa88215498
Signed-off-by: John Hammond <jhammond@tacc.utexas.edu>
Signed-off-by: Richard Henwood <rhenwood@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1094
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>