staging/lustre: 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>