kernel: Workaround for double lock of spinlock in user timers.

The thread that is being [un]scheduled already has its time_lock locked
in {stop|continue}_cpu_timers(). When updating the TeamTimeUserTimer,
the team is asked for its cpu time. Team::CPUTime() then iterates the
threads of the team and locks the time_lock of the thread again.

This workaround passes a possibly locked thread through the relevant
functions so Team::CPUTime() can decide whether or not a thread it
iterates needs to be locked or not.

This works around #11032 and its duplicates #11314 and #11344.

headers/private/kernel/UserTimer.h

@@ -117,14 +117,16 @@ struct TeamTimeUserTimer : public UserTimer {
 
 			void				Deactivate();
 
-			void				Update(Thread* unscheduledThread);
+			void				Update(Thread* unscheduledThread,
+									Thread* lockedThread = NULL);
 			void				TimeWarped(bigtime_t changedBy);
 
 protected:
 	virtual	void				HandleTimer();
 
 private:
-			void				_Update(bool unscheduling);
+			void				_Update(bool unscheduling,
+									Thread* lockedThread = NULL);
 
 private:
 			team_id				fTeamID;