syscalls/clone08: skip CLONE_STOPPED for kernel >= 2.6.38

According to clone(2) manual page "This flag was deprecated from
Linux 2.6.25 onward, and was removed altogether in Linux 2.6.38."
Skip test_clone_stopped() test for kernel >= 2.6.38.

Signed-off-by: Shuang Qiu <shuang.qiu@oracle.com>
Signed-off-by: Jan Stancek <jstancek@redhat.com>