LU-8888 clio: remove unused members from struct cl_thread_info

LU-8888 clio: remove unused members from struct cl_thread_info

The pointer to the topmost ongoing IO in the thread and
other members are not used any more.

Change-Id: I4875fe7d0e5f64fd3a4a60fc1bd1877c9d6e3340
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: https://review.whamcloud.com/24062
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>