LU-8066 obdclass: Get rid of remaining /proc/sys/lustre plumbing

LU-8066 obdclass: Get rid of remaining /proc/sys/lustre plumbing

Since all of the variables from /proc/sys/lustre were moved to
/sys/fs/lustre, get rid of the remaining infrastructure.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Change-Id: I6facdb8f52b86efb1e85a4d43ca2532a2f460a85
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/24034
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Tested-by: Oleg Drokin <oleg.drokin@intel.com>