LU-709 build: clean up quota_read, follow_link and RCU

LU-709 build: clean up quota_read, follow_link and RCU

1. super_operations.quota_read exists since v2.6.12
2. inode_operations->follow_link returns a cookie since v2.6.13
3. RCU exists since v2.6.12

Signed-off-by: Peng Tao <tao.peng@emc.com>
Change-Id: Id79df5dcb0e3db9eb424337fd71d896ed8fefcd6
Reviewed-on: http://review.whamcloud.com/2316
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>