Partially revert the previous change. I failed to notice that where

Partially revert the previous change.  I failed to notice that where
ktruserret() is invoked, an unlocked check of  the per-process queue
is performed inline, thus, we don't lock the ktrace_sx on every userret().

Pointy hat to:	jhb
Approved by:	re (kensmith)
Pointy hat recovered from:	rwatson