On IRC on 2015-09-28:

  11:28 < jojy_mesos> i guess i was expecting an additional attribute
    for hooks that specifies whether the hooks runs in the host
    namespace or in the container's namespace
  11:28 < lk4d4> they all run in host namespaces

Signed-off-by: W. Trevor King <wking@tremily.us>

And explain how the handling differs when a new start-call joins an
existing container vs. creating a new container.  This is spun off
from the mailing list thread now that that's settled down [1].

This write-up is just about Linux containers, since I don't understand
the other systems well enough to do them justice.

[1]: https://groups.google.com/a/opencontainers.org/forum/#!topic/dev/frUXLljXy8Y
     Message-ID: <20150915034717.GO18018@odin.tremily.us>

Signed-off-by: W. Trevor King <wking@tremily.us>

These just landed via opencontainers#202.  I'm not entirely clear on how we intend
to handle "the application died before we finished executing post-stop
hooks", but I've made my best guess here.

Signed-off-by: W. Trevor King <wking@tremily.us>