Reduces log level of auth error lines from error->warn
Reduces log level of auth error lines from error->warn

An error level log is already produced within app.authorized() if an
actual unexpected error occurs during authorization, so this warning
level log remains for auditability purposes, but should not be
considered an error condition.

Addresses #704

Signed-off-by: Brian Bland <5edcc1e68a17b4ff3b55c6007615b6004b1df064@docker.com>

tdooner/distribution,linearregression/distribution,thaJeztah/docker.github.io,denverdino/distribution,Tiesheng/distribution,yuwaMSFT2/distribution,andrewnguyen/distribution,gdevillele/docker.github.io,denverdino/distribution,LuisBosquez/docker.github.io,sebrandon1/distribution,aduermael/docker.github.io,jackpgriffin/distribution,imranraja85/distribution,jramseye/distribution,hopkings2008/distribution,tian-xiaobo/distribution,LouisKottmann/distribution,arvindkandhare/distribution,BrickXu/distribution,bdwill/docker.github.io,wangmingshuai/distribution,paulczar/distribution,konnase/distribution,gavioto/distribution,13W/distribution,aaronlehmann/distribution,manoj535/distribution,mbentley/distribution,13W/distribution,avinson/distribution,djenriquez/distribution,sanscontext/docker.github.io,bigsurge/distribution,vdemeester/distribution,endophage/distribution,sergeyfd/distribution,shin-/docker.github.io,mikebrow/distribution,BrianBland/distribution,noxiouz/distribution,CodeJuan/distribution,bigsurge/distribution,yuwaMSFT2/distribution,arneluehrs/distribution,ContainerSolutions/distribution,bsmr-docker/distribution,atyenoria/distribution,curtiszimmerman/distribution,joaofnfernandes/docker.github.io,duglin/distribution,BradleyA/distribution,hpcloud/distribution,BSWANG/denverdino.github.io,kmala/distribution,spacexnice/distribution,konstruktoid/distribution,zerosign/distribution,jhicks-camgian/distribution,anweiss/docker.github.io,stevvooe/distribution,jmitchell/distribution,BradleyA/distribution,nateww/distribution,dobril-stanga/distribution,phiroict/docker,thelinuxkid/distribution,Gobliip/distribution,denverdino/denverdino.github.io,docker-zh/docker.github.io,tschoots/distribution,rillig/docker.github.io,calavera/distribution,bdwill/docker.github.io,rillig/docker.github.io,joaofnfernandes/docker.github.io,miminar/distribution,bxy09/distribution,rodacom/docker-hub,thaJeztah/docker.github.io,konnase/distribution,joaofnfernandes/docker.github.io,lindenlab/distribution,humble00/distribution,aibaars/distribution,schu/distribution,londoncalling/docker.github.io,beni55/distribution,troy0820/docker.github.io,menglingwei/denverdino.github.io,harche/distribution,n1tr0g/distribution,jramseye/distribution,jzwlqx/distribution,joeuo/docker.github.io,nwt/distribution,joeuo/docker.github.io,nevermosby/distribution,londoncalling/docker.github.io,rochacon/distribution,mattrgreen/distribution,anweiss/docker.github.io,jordimassaguerpla/distribution,menglingwei/denverdino.github.io,dalanlan/distribution,LuisBosquez/docker.github.io,avinson/distribution,aprajshekhar/distribution,sanscontext/docker.github.io,championv/distribution,tian-xiaobo/distribution,ChenLingPeng/distribution,arvindkandhare/distribution,jonboulle/distribution,iskradelta/distribution,johnstep/docker.github.io,JimGalasyn/docker.github.io,manoj535/distribution,Seb-Solon/distribution,linearregression/distribution,Gobliip/distribution,aprajshekhar/distribution,tschoots/distribution,danix800/docker.github.io,vdemeester/distribution,BSWANG/denverdino.github.io,liubin/distribution,jordimassaguerpla/distribution,anweiss/docker.github.io,thaJeztah/docker.github.io,codefresh-io/cf-distribution,jzwlqx/denverdino.github.io,nevermosby/distribution,jonboulle/distribution,arneluehrs/distribution,bpradipt/distribution,tdooner/distribution,docker-zh/docker.github.io,alexisbellido/docker.github.io,shubheksha/docker.github.io,shin-/docker.github.io,shin-/docker.github.io,danix800/docker.github.io,liubin/distribution,andrewnguyen/distribution,jzwlqx/distribution,huamai-io/distribution,harrisonfeng/distribution,docker/docker.github.io,jlhawn/distribution,baloo/distribution,docker/docker.github.io,deis/distribution,denverdino/docker.github.io,docker-zh/docker.github.io,jrjang/distribution,hpcloud/distribution,troy0820/docker.github.io,Tiesheng/distribution,curtiszimmerman/distribution,phiroict/docker,johnstep/docker.github.io,lindenlab/distribution,amitshukla/distribution,JimGalasyn/docker.github.io,johnstep/docker.github.io,lcarstensen/distribution,imranraja85/distribution,xiekeyang/distribution,paulczar/distribution,alexisbellido/docker.github.io,genedock/distribution,shin-/docker.github.io,phiroict/docker,BSWANG/denverdino.github.io,gdevillele/docker.github.io,Seb-Solon/distribution,harche/distribution,tt/distribution,aduermael/docker.github.io,denverdino/denverdino.github.io,duglin/distribution,jwhonce/distribution,convox/distribution,alexisbellido/docker.github.io,shyr/distribution,humble00/distribution,docker-zh/docker.github.io,denverdino/distribution-stevvooe,endophage/distribution,docker/docker.github.io,baloo/distribution,mattrgreen/distribution,lcarstensen/distribution,denverdino/docker.github.io,armbuilds/distribution,AoJ/distribution,denverdino/docker.github.io,alexisbellido/docker.github.io,sanscontext/docker.github.io,JimGalasyn/docker.github.io,joeuo/docker.github.io,moxiegirl/distribution,jzwlqx/denverdino.github.io,estesp/distribution,BrickXu/distribution,sthapaun/dist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