staging/lustre/libcfs: remove CAPABILITY_VERSION tests

_LINUX_CAPABILITY_VERSION is only for backward compatibility in
user space. Kernel code doesn't care about it.

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