cppcheck: Fixes issue found in DiagsConfig.cc
cppcheck: Fixes issue found in DiagsConfig.cc

Member variable 'DiagsConfig::diags' is not initialized in the constructor.

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