[Openib-windows] CM and timewait

[Tillier, Fabian]

Should the CM enforce timewait at the QP level?  That is, should QP
modifications fail while a QP is in timewait?

The current gen2 Linux CM does not do this.  The existing IBAL CM does.
The new CM in fab_cm_branch does for kernel QPs, but not for UM QPs,
which is silly.  Kernel clients should be trusted, and user-mode should
not, so either we should just drop it because timewait is generally so
darn fast, or we need to enforce it for UM clients.

The timewait would still be tracked in the CM at the connection endpoint
level.  Obviously, removing tracking at the QP level is much easier than
adding support to properly track it for UM QPs.

Also, removing the interaction allows decoupling the CM from the QP a
little more, and paves the way to exposing the CM's internal API to
clients which would match the Linux usage model more closely.

So what do y'all think?  Enforce or ditch timewait at the QP level?

Thanks,

- Fab