pidns16: split test condition and result judge

Make it easy to read.

Signed-off-by: Monson Shao <jshao@redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
pidns16: modified test results

The test should result TFAIL if child is signalled from unexpected pid,
instead of TBROK. The same as TPASS/TINFO .

Signed-off-by: Monson Shao <jshao@redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
pidns16: child should not get parent pid in parent NS

parent pid in parent NS is invisible to child, even when child got signalled
from parent, the signaller process should be fake parent (PID 0).

Signed-off-by: Monson Shao <jshao@redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>