QNIC-based, fully blocking circuit switching

[rdviii]

Simplest form: first message processed sets a flag that the QNIC is busy. Issue: how do we make sure we don't get conflicting reservations at the two ends of the link? Allow a request to sit unprocessed until the connection that first got the link finishes. How do we do that? Can we set an event?

[rdviii]

Thinking about this, can't just wait passively, we might deadlock. When a request fails to allocate a resource, we have to tear down the entire set of reservations so far, then sleep for some random period of time, then try again.

[rdviii]

One set of notes available at https://hackmd.io/ruP6-gCmQh6zoApdXz8DRw?view

[rdviii]

Duplicate of #55

[Chibikuri]

Need release qnic