doc: fix a typo in traffic_via command reference
doc: fix a typo in traffic_via command reference

This closes #404.

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