Retry freeze in cgroups TasksKiller to workaround MESOS-1689.

Review: https://reviews.apache.org/r/24511
Added overloads to 'process::defer()' to dispatch lambda function
to a specific pid.
Added authorization support for "/shutdown" endpoint and updated
ACLs format.
Add ContainerInfo and Volumes proto defs

Review: https://reviews.apache.org/r/24349