Revert "kernel - Reduce priority range from dynamic priority"

Revert "kernel - Reduce priority range from dynamic priority"

This reverts commit abc0cda7b4a0a92afab15645d5adfac57af02866.

The change improved how nice ranging works but completely blew up
fork priority reduction, causing parent process dispatches via
fork/exec (such as done by a service or by make) to not immediately
move the child proces to another cpu when the parent has more work
to do.

This caused the kernel build to regress from 3:12 to 3:21 on the
test box, and for the world build to only show minor improvements
instead of more significant improvements.

So revert it for now.  We will improve nice priorities another way.