kernel - Add usched_dfly algorith, set as default for now (4)
* Fix fork regression with usched_dfly. Most fork/exec sequences involve
the parent waiting. The new scheduler was placing the newly forked
process on another cpu which is non-optimal if the parent is going
to immediately wait.
Instead if there is nothing else waiting to run on the current cpu,
leave the forked process on the current cpu initially. If the parent
waits quickly the forked process will get cpu, otherwise it will get
scheduled away soon enough. If the parent forks additional children
then we find there is something on the queue now (the first child) and
put the additional children on other cpus.
Reported-by: thesjg