LU-3963 libcfs: convert md[d/t]/mg[c/s] to linux atomic primitives

LU-3963 libcfs: convert md[d/t]/mg[c/s] to linux atomic primitives

This patch convers all cfs_atomic primitives in
mdd, mdt, mgc and mgs.

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: I052ca4da80b0cbd36df02a50f2ae0651eec28ea8
Reviewed-on: http://review.whamcloud.com/7074
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>