staging/lustre/obdclass: move obd_sysctl_init out of class_procfs_init

It is not strictly related to procfs. Besides, we already call obd_sysctl_clean
outside of class_procfs_clean.

Signed-off-by: Peng Tao <bergwolf@gmail.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>