 - Add an implementation of sched_preempt() that avoids excessive IPIs.  - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt()    so the logical is identical and not repeated between tdq_notify() and    sched_setpreempt().  - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock    this could have caused us to lose td_flags settings.  - Garbage collect some tunables that are no longer relevant.
 - Add an implementation of sched_preempt() that avoids excessive IPIs.
 - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt()
   so the logical is identical and not repeated between tdq_notify() and
   sched_setpreempt().
 - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock
   this could have caused us to lose td_flags settings.
 - Garbage collect some tunables that are no longer relevant.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase