LU-985 lprocfs: verify user buffer access

LU-985 lprocfs: verify user buffer access

In lprocfs_xxx_evict_client(), need verify user's buffer when access
it.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: I702e22f8d432edce200c6d91a0af8a1eac792008
Reviewed-on: http://review.whamcloud.com/1961
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Liang Zhen <liang@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>