sigaction:16-1: leave it untested on the Linux kernel less than 2.6.22

As the Linux signal(7) said:
POSIX semaphore interfaces: sem_wait(3) and sem_timedwait(3) (since Linux 2.6.22; beforehand, always failed with EINTR).

So, on Linux, we just leave it untested when the kernel version
is less than 2.6.22 and user wants to filter it.

Signed-off-by: Peng Haitao <penght@cn.fujitsu.com>
Signed-off-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
open_posix_testsuite: Update document

Suggested-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Peng Haitao <penght@cn.fujitsu.com>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>