Clarify postStart
Clarify postStart

As Brendan Burns explained me in this email:
https://groups.google.com/forum/#!topic/google-containers/5eUsmTSXpb8

AlainRoy/alainroy.github.io,erictune/erictune.github.io,erictune/erictune.github.io,erictune/erictune.github.io,rata/kubernetes.github.io,rata/kubernetes.github.io,aidevops/kubernetes.github.io,AlainRoy/alainroy.github.io,ronaldpetty/kubernetes.github.io,ronaldpetty/kubernetes.github.io,erictune/erictune.github.io,aidevops/kubernetes.github.io,aidevops/kubernetes.github.io,ronaldpetty/kubernetes.github.io,AlainRoy/alainroy.github.io,rata/kubernetes.github.io,rata/kubernetes.github.io,rata/kubernetes.github.io,aidevops/kubernetes.github.io,aidevops/kubernetes.github.io,erictune/erictune.github.io