LU-1240 iokit: fix incorrect statement in README

file_count should be per thread

Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Change-Id: I656d53417a529025f863622036ee51fbbfb4364b
Reviewed-on: http://review.whamcloud.com/2464


Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Richard Henwood <rhenwood@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>