When the watchdog thread exits it runs through the exit path with FIFO
priority. There is no point in doing so. Switch back to SCHED_NORMAL
before exiting.

Cc: Don Zickus <dzickus@redhat.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1109121337461.2723@ionosSigned-off-by: NIngo Molnar <mingo@elte.hu>