Ping[2]: [PATCH] Fix sporadic failure in tst-eintr1 test case

[KOSAKI Motohiro]

>> Ping:
>>
>> http://sourceware.org/ml/libc-alpha/2012-09/msg00538.html
>
> ping again!

I'm not sure 'write (STDOUT_FILENO, "!", 1)' is a good idea. but I'm
sure this race can be happen and we need to check EAGAIN. so I
think this patch is correct.

I have a question. Do any standard require pthread_join() ensure to
reduce NPROC? I guess no.