Handled EINTR for waitpid in ChildHook::SUPERVISOR from subprocess.
Handled EINTR for waitpid in ChildHook::SUPERVISOR from subprocess.

If `waitpid` fails due to `EINTR`, we need to retry.

Review: https://reviews.apache.org/r/60704/

kaysoky/mesos,neilconway/mesos,reneploetz/mesos,asamerh4/mesos,zmalik/mesos,Gilbert88/mesos,abudnik/mesos,neilconway/mesos,verizonlabs/mesos,gsantovena/mesos,andschwa/mesos,Gilbert88/mesos,dforsyth/mesos,zmalik/mesos,abudnik/mesos,gsantovena/mesos,dforsyth/mesos,kaysoky/mesos,verizonlabs/mesos,abudnik/mesos,chhsia0/mesos,asamerh4/mesos,abudnik/mesos,dforsyth/mesos,Gilbert88/mesos,kaysoky/mesos,reneploetz/mesos,jpeach/mesos,zmalik/mesos,verizonlabs/mesos,zmalik/mesos,andschwa/mesos,neilconway/mesos,Gilbert88/mesos,abudnik/mesos,gsantovena/mesos,reneploetz/mesos,verizonlabs/mesos,chhsia0/mesos,verizonlabs/mesos,andschwa/mesos,andschwa/mesos,Gilbert88/mesos,gsantovena/mesos,jpeach/mesos,zmalik/mesos,abudnik/mesos,jpeach/mesos,neilconway/mesos,dforsyth/mesos,reneploetz/mesos,chhsia0/mesos,chhsia0/mesos,dforsyth/mesos,neilconway/mesos,jpeach/mesos,andschwa/mesos,gsantovena/mesos,asamerh4/mesos,Gilbert88/mesos,asamerh4/mesos,zmalik/mesos,chhsia0/mesos,reneploetz/mesos,asamerh4/mesos,reneploetz/mesos,kaysoky/mesos,neilconway/mesos,asamerh4/mesos,asamerh4/mesos,jpeach/mesos,kaysoky/mesos,Gilbert88/mesos,kaysoky/mesos,jpeach/mesos,reneploetz/mesos,neilconway/mesos,andschwa/mesos,zmalik/mesos,gsantovena/mesos,dforsyth/mesos,chhsia0/mesos,dforsyth/mesos,andschwa/mesos,kaysoky/mesos,verizonlabs/mesos,jpeach/mesos,chhsia0/mesos,verizonlabs/mesos,abudnik/mesos,gsantovena/mesos