More ULE bugs fixed.

[Jeff Roberson]

I fixed two bugs that were exposed due to more of the kernel running
outside of Giant.  ULE had some issues with priority propagation that
stopped it from working very well.

Things should be much improved.  Feedback, as always, is welcome.  I'd
like to look into making this the default scheduler for 5.2 if things
start looking up.  I hope that scares you all into using it more. :-)

Cheers,
Jeff