LU-10934 tests: fix compilation without SELINUX

LU-10934 tests: fix compilation without SELINUX

lustre/tests/statx.c does not compile is SELINUX support
is not installed.
So add some #ifdefs to fix it.

Test-Parameters: trivial
Fixes: 3f7853b31ef6 ("LU-10934 llite: integrate statx() API with Lustre")
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Ia0f285e1bb04270aff753bea71ffbe15a911db5f
Reviewed-on: https://review.whamcloud.com/38973
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Yingjin Qian <qian@ddn.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>