Add the limitation of the nested container id length

Hi, I am working on the issue MESOS-7168, to limit the nested container id length. Considering the AUFS case [1] (thanks, Andy for pointing it out), we should set the nested containerID limit to 242. Please let me know if you have any concern. [1]

Proposing Minimum Capability to Safeguard Downgrade

Hi: A common use case for downgrade is rolling back from problematic upgrades. Mesos promises compatibility between any 1.x and 1.y versions of masters/agents as long as new features are not used. However, currently there is no easy way to tell whether any “new” features are being used. And any

Re: Should we remove `noexcept` from `ObjectApprover::approved()` signature?

Hi, I still believe that declaring methods of this module interface `except` is a good thing which IMO we should also do for all new module interfaces going forward. We do not perform any exception handling around calls to these functions in Mesos, and `noexcept` is intended to communicate