Current code isn't very correct: because Linux signal system design
follows SysV Unix behavior, when a SIGCHLD happens, it only means there
are child programs died (either self-quit or involuntarily killed, from
wstatus may figure out), linux kernel only deliver SIGCHLD once to parent
before the parent process;
so when SIGCHLD happens, you don't know is that one child only or more
so the code need a loop until wait4 returns zero, at rumtime got this:
```console
2017/07/14 21:14:32 reap dead child: 579, wstatus: 0x00000000
2017/07/14 21:14:32 reap dead child: 580, wstatus: 0x00000000
2017/07/14 21:14:32 reap dead child: 583, wstatus: 0x00000000
```
then in the container there are no more zombies. final resolve#26
mr c0b
codeskyblue