LU-8066 lod: replace class_process_proc_param()

LU-8066 lod: replace class_process_proc_param()

With the move to sysfs for lod every lctl conf_param option will
send out a udev event. Replace class_process_proc_param() with
class_modify_config() so sysfs attributes can be set directly.

This patch exposed an error in stripecount_store() which doesn't
allow setting stripe count to -1 which is wrong.

Change-Id: I4eee8b2b0f3661ac69242ff7a1da6346153a56e8
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/33180
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>