LU-3963 libcfs: convert obdecho,obdclass code to atomics

LU-3963 libcfs: convert obdecho,obdclass code to atomics

This patch converts all cfs_atomic primitives in
target, obdclass and obdecho.

Signed-off-by: Liu Xuezhao <xuezhao.liu@emc.com>
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Change-Id: I6ab6d7a476f5192e6bdfb39d4956361ce2b3e987
Reviewed-on: http://review.whamcloud.com/7075
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>