Concerning master's validation of ExecutorID upon slave reregistration

[James DeFelice <ja...@gmail.com>]

I've filed a JIRA for it here:
https://issues.apache.org/jira/browse/MESOS-8169

The change I'm proposing would change validation (for slave reregistration)
to only enforce ExecutorID uniqueness in the context of (FrameworkID,
SlaveID) as opposed to simply SlaveID as currently implemented.

This change might cause trouble for any frameworks that expect ExecutorID
to be unique across every non-terminal executor for every framework running
on a given slave. That said, ExecutorID is a framework-generated ID and so
it's uniqueness *should* be scoped to a framework to begin with.

Please comment on the linked JIRA if you're concerned about the proposed
change.

Thanks,
James