LU-6943 clio: get rid of cl_req

LU-6943 clio: get rid of cl_req

Implement cl_req_attr_set with a cl_object operation.
Get rid of cl_req and related function and data structures.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: I7ea4af3eed65c312835e19f12dd01c7c87445352
Reviewed-on: http://review.whamcloud.com/15833
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>