Fix default logging.yaml with new format.
Fix default logging.yaml with new format.

'logging' is the toplevel key

duke8253/trafficserver,dyrock/trafficserver,SolidWallOfCode/trafficserver,pbchou/trafficserver,davidbz/trafficserver,bryancall/trafficserver,SolidWallOfCode/trafficserver,dyrock/trafficserver,SolidWallOfCode/trafficserver,davidbz/trafficserver,vmamidi/trafficserver,davidbz/trafficserver,pbchou/trafficserver,dyrock/trafficserver,bryancall/trafficserver,vmamidi/trafficserver,SolidWallOfCode/trafficserver,dyrock/trafficserver,vmamidi/trafficserver,duke8253/trafficserver,duke8253/trafficserver,dyrock/trafficserver,dyrock/trafficserver,pbchou/trafficserver,davidbz/trafficserver,bryancall/trafficserver,davidbz/trafficserver,duke8253/trafficserver,duke8253/trafficserver,pbchou/trafficserver,pbchou/trafficserver,bryancall/trafficserver,vmamidi/trafficserver,pbchou/trafficserver,duke8253/trafficserver,vmamidi/trafficserver,dyrock/trafficserver,SolidWallOfCode/trafficserver,SolidWallOfCode/trafficserver,duke8253/trafficserver,bryancall/trafficserver,vmamidi/trafficserver,davidbz/trafficserver,SolidWallOfCode/trafficserver,bryancall/trafficserver