update docs for background fetch exclude config file
update docs for background fetch exclude config file

rpufky/trafficserver,pbchou/trafficserver,chitianhao/trafficserver,reveller/trafficserver,reveller/trafficserver,persiaAziz/trafficserver,rpufky/trafficserver,taoyunxing/trafficserver,chenglongwei/trafficserver,vmamidi/trafficserver,rahmalik/trafficserver,bryancall/trafficserver,bryancall/trafficserver,pbchou/trafficserver,rahmalik/trafficserver,chenglongwei/trafficserver,rahmalik/trafficserver,clearswift/trafficserver,duke8253/trafficserver,vmamidi/trafficserver,persiaAziz/trafficserver,SolidWallOfCode/trafficserver,reveller/trafficserver,clearswift/trafficserver,PSUdaemon/trafficserver,PSUdaemon/trafficserver,davidbz/trafficserver,persiaAziz/trafficserver,bryancall/trafficserver,rpufky/trafficserver,taoyunxing/trafficserver,davidbz/trafficserver,SolidWallOfCode/trafficserver,SolidWallOfCode/trafficserver,chenglongwei/trafficserver,clearswift/trafficserver,PSUdaemon/trafficserver,SolidWallOfCode/trafficserver,PSUdaemon/trafficserver,reveller/trafficserver,chitianhao/trafficserver,vmamidi/trafficserver,vmamidi/trafficserver,dyrock/trafficserver,chenglongwei/trafficserver,taoyunxing/trafficserver,vmamidi/trafficserver,chitianhao/trafficserver,rahmalik/trafficserver,rpufky/trafficserver,taoyunxing/trafficserver,bryancall/trafficserver,duke8253/trafficserver,chenglongwei/trafficserver,vmamidi/trafficserver,reveller/trafficserver,SolidWallOfCode/trafficserver,rahmalik/trafficserver,rahmalik/trafficserver,taoyunxing/trafficserver,rpufky/trafficserver,duke8253/trafficserver,chitianhao/trafficserver,SolidWallOfCode/trafficserver,chenglongwei/trafficserver,davidbz/trafficserver,duke8253/trafficserver,chenglongwei/trafficserver,reveller/trafficserver,dyrock/trafficserver,persiaAziz/trafficserver,clearswift/trafficserver,rpufky/trafficserver,dyrock/trafficserver,chenglongwei/trafficserver,rahmalik/trafficserver,PSUdaemon/trafficserver,rpufky/trafficserver,duke8253/trafficserver,persiaAziz/trafficserver,dyrock/trafficserver,clearswift/trafficserver,duke8253/trafficserver,PSUdaemon/trafficserver,clearswift/trafficserver,dyrock/trafficserver,chitianhao/trafficserver,taoyunxing/trafficserver,taoyunxing/trafficserver,clearswift/trafficserver,rahmalik/trafficserver,pbchou/trafficserver,rpufky/trafficserver,reveller/trafficserver,dyrock/trafficserver,reveller/trafficserver,pbchou/trafficserver,chitianhao/trafficserver,pbchou/trafficserver,bryancall/trafficserver,reveller/trafficserver,rpufky/trafficserver,clearswift/trafficserver,PSUdaemon/trafficserver,chitianhao/trafficserver,clearswift/trafficserver,davidbz/trafficserver,PSUdaemon/trafficserver,persiaAziz/trafficserver,duke8253/trafficserver,davidbz/trafficserver,bryancall/trafficserver,dyrock/trafficserver,taoyunxing/trafficserver,SolidWallOfCode/trafficserver,PSUdaemon/trafficserver,taoyunxing/trafficserver,persiaAziz/trafficserver,persiaAziz/trafficserver,rahmalik/trafficserver,davidbz/trafficserver,pbchou/trafficserver