small nit: fix unmeaningful log
small nit: fix unmeaningful log

Truncated dir name can't give any useful information, print whole dir
name will.

Bad debug log is like this:

```
DEBU[2449] aufs error unmounting /var/lib/doc: no such file or directory
```

Signed-off-by: Zhang Wei <14976e959b2860fb06a3c1edbdb1945a4e11b8b5@huawei.com>

AkihiroSuda/docker,jhorwit2/docker,darrenstahlmsft/moby,laijs/moby,docker/docker,rhatdan/docker,erikstmartin/docker,danyalKhaliq10p/moby,rhatdan/docker,JMesser81/docker,Syntaxide/docker,jvanz/docker,KingEmet/docker,thtanaka/docker,yongtang/docker,moby/moby,cpuguy83/docker,moby/moby,kencochrane/docker,konstruktoid/docker-upstream,prertik/docker,PatrickLang/moby,nalind/docker,dccurtis/docker,tmp6154/docker,sdurrheimer/docker,ripcurld0/moby,harche/docker,naveed-jamil-tenpearls/moby,mstanleyjones/docker,sfsmithcha/docker,nawawi/docker,Ramzec/docker,tklauser/docker,konstruktoid/docker-1,johnstep/moby-moby,charleszheng44/moby,tianon/docker,crosbymichael/docker,liaoqingwei/docker,KarthikNayak/docker,eskaaren/docker,mtrmac/docker,Syntaxide/docker,kojiromike/docker,pradipd/moby,dims/docker,cyphar/docker,estesp/docker,kunalkushwaha/docker,Mokolea/docker,imkin/moby,icaoweiwei/docker,dmcgowan/docker,thtanaka/docker,erikh/docker,dperny/docker,q384566678/docker,harche/docker,maxamillion/docker,thaJeztah/docker,mtanlee/docker,SvenDowideit/docker,raja-sami-10p/moby,mixja/docker,haveatry/docker,gnailuy/docker,catinthesky/docker,cpuguy83/docker,bearstech/moby,shishir-a412ed/docker,nalind/docker,sarnautov/moby,coolljt0725/docker,lixiaobing1/docker,13W/docker,jimjag/docker,dsheets/moby,hypriot/docker,mkumatag/docker,djs55/docker,thaJeztah/docker,x1022as/docker,imkin/moby,yosifkit/docker,kojiromike/docker,dims/docker,KingEmet/docker,coreos/docker,brahmaroutu/docker,prertik/docker,tophj-ibm/moby,konstruktoid/docker-1,tonistiigi/docker,hqhq/moby,darrenstahlmsft/moby,ndeloof/docker,rremer/moby,moul/docker,danyalKhaliq10p/moby,Ramzec/docker,HuKeping/docker,johnstep/moby-moby,jthelin/docker,miminar/docker,dongjoon-hyun/docker,icaoweiwei/docker,tonistiigi/docker,jhorwit2/docker,paralin/docker,coolljt0725/docker,twaugh/docker,dmcgowan/docker,whuwxl/docker,splunk/docker,lixiaobing1/docker,charleszheng44/moby,mohmost12/docker,portworx/docker,mohmost12/docker,rremer/moby,xiaods/docker,vdemeester/docker,HuKeping/docker,diogomonica/docker,srust/docker,afein/docker,vdemeester/docker,qudongfang/docker,darrenstahlmsft/docker,kolyshkin/moby,xiekeyang/docker,madhanrm/docker,dmcgowan/docker,ColinHebert/docker,AkihiroSuda/docker,mkumatag/docker,cloudflare/docker,portworx/docker,moypray/docker,yasiramin10p/moby,icaoweiwei/docker,shishir-a412ed/docker,naveed-jamil-tenpearls/moby,endophage/docker,shishir-a412ed/docker,konstruktoid/docker-upstream,haveatry/docker,msabansal/docker,mike1729/docker,darrenstahlmsft/docker,mikedougherty/docker,sfsmithcha/docker,tmp6154/docker,unclejack/docker,duglin/docker,mahak/docker,docker/docker,yasiramin10p/moby,13W/docker,stevvooe/docker,13W/docker,flavio/docker,bearstech/moby,erikstmartin/docker,YuPengZTE/docker,ajaymdesai/docker,tonistiigi/docker,laijs/docker,whuwxl/docker,ColinHebert/docker,Ramzec/docker,tophj-ibm/moby,gnailuy/docker,fcrisciani/docker,PatrickLang/moby,YuPengZTE/docker,tklauser/docker,dccurtis/docker,yosifkit/docker,dgageot/docker,laijs/moby,imkin/moby,gnailuy/docker,jlhawn/docker,tklauser/docker,miminar/docker,raja-sami-10p/moby,flavio/docker,tophj-ibm/docker,mikedougherty/docker,hypriot/docker,splunk/docker,ajaymdesai/docker,erikh/docker,hypriot/docker,noironetworks/docker,sterchelen/docker,pramodhkp/moby,moul/docker,laijs/docker,yosifkit/docker,tophj-ibm/docker,thaJeztah/docker,justincormack/docker,amatsus/docker,q384566678/docker,HuKeping/docker,vdemeester/docker,fcrisciani/docker,nalind/docker,msabansal/docker,allencloud/docker,kolyshkin/docker,kencochrane/docker,bonczj/moby-json-file-logger,mahak/docker,yp-engineering/docker,KarthikNayak/docker,duglin/docker,jimjag/docker,HideoYamauchi/docker,yummypeng/docker,jameszhan/docker,diogomonica/docker,sdurrheimer/docker,thaJeztah/docker,amatsus/docker,cpuguy83/docker,bearstech/moby,nalind/docker,Mokolea/docker,eskaaren/docker,michael-holzheu/docker,Ramzec/docker,resin-io/docker,nawawi/docker,yongtang/docker,dongjoon-hyun/docker,unclejack/docker,kolyshkin/moby,djs55/docker,paralin/docker,estesp/docker,POLJM242/docker,hqhq/moby,kolyshkin/docker,scotttlin/docker,13W/docker,dsheets/moby,dongjoon-hyun/docker,laijs/moby,mixja/docker,tophj-ibm/moby,tagomoris/docker,Mokolea/docker,moul/docker,yongtang/docker,rancher/docker,ibuildthecloud/docker,raja-sami-10p/moby,kolyshkin/moby,lixiaobing10051267/docker,alfred-landrum/docker,portworx/docker,estesp/docker,rancher/docker,jimjag/docker,mstanleyjones/docker,msabansal/docker,gjaskiewicz/moby,charleszheng44/moby,moypray/docker,gjaskiewicz/moby,duglin/docker,eskaaren/docker,mtesselH/docker,ndeloof/docker,jameszhan/docker,thtanaka/docker,x1022as/docker,ajaymdesai/docker,darrenstahlmsft/moby,lixiaobing1/docker,erikstmartin/docker,q384566678/docker,endophage/docker,jlhawn/docker,Mokolea/docker,mahak/docker,shhsu/docker,kencochrane/docker,ripcurld0/moby,mikebrow/docker,ffoysal/docker,liaoqingwei/docker,flavio/docker,amatsus/docker,jlhawn/docker,jhorwit2/docker,sarnautov/moby,mstanleyjones/docker,KingEmet/docker,ffoysal/docker,moypray/docker,michael-holzheu/docker,jwhonce/docker,jameszhan/docker,resin-io/docker,jimjag/docker,ibuildthecloud/docker,yummypeng/docker,jthelin/docker,yp-engineering/docker,SvenDowideit/docker,JMesser81/docker,scotttlin/docker,POLJM242/docker,dgageot/docker,catinthesky/docker,mikebrow/docker,harche/docker,gnailuy/docker,splunk/docker,YuPengZTE/docker,fcrisciani/docker,maxamillion/docker,mtanlee/docker,sfsmithcha/docker,sdurrheimer/docker,madhanrm/docker,mtrmac/docker,yasiramin10p/moby,flavio/docker,mtanlee/docker,johnstep/moby-moby,kunalkushwaha/docker,yosifkit/docker,unclejack/docker,SvenDowideit/docker,HideoYamauchi/docker,tmp6154/docker,jvanz/docker,bonczj/moby-json-file-logger,asbjornenge/docker,cpuguy83/docker,mohmost12/docker,laijs/docker,konstruktoid/docker-1,endophage/docker,srust/docker,JMesser81/docker,hqhq/moby,dgageot/docker,tagomoris/docker,gschaetz/moby,naveed-jamil-tenpearls/moby,13W/docker,afein/docker,kunalkushwaha/docker,gschaetz/moby,allencloud/docker,catinthesky/docker,mikebrow/docker,brahmaroutu/docker,mike1729/docker,stevvooe/docker,prertik/docker,pradipd/moby,xiekeyang/docker,jwhonce/docker,xiaods/docker,justincormack/docker,whuwxl/docker,madhanrm/docker,jwhonce/docker,michelvocks/docker,xiekeyang/docker,michelvocks/docker,noironetworks/docker,rhatdan/docker,lixiaobing10051267/docker,cloudflare/docker,danyalKhaliq10p/moby,liaoqingwei/docker,asbjornenge/docker,moul/docker,alfred-landrum/docker,twaugh/docker,miminar/docker,AkihiroSuda/docker,ColinHebert/docker,bonczj/moby-json-file-logger,dims/docker,pradipd/moby,yummypeng/docker,xiaods/docker,nawawi/docker,paralin/docker,coreos/docker,x1022as/docker,scotttlin/docker,pramodhkp/moby,dccurtis/docker,coreos/docker,dperny/docker,ripcurld0/moby,HideoYamauchi/docker,tianon/docker,djs55/docker,mikedougherty/docker,crosbymichael/docker,akira-baruah/docker,pramodhkp/moby,mkumatag/docker,ibuildthecloud/docker,sarnautov/moby,afein/docker,mixja/docker,qudongfang/docker,gjaskiewicz/moby,brahmaroutu/docker,Syntaxide/docker,xuxinkun/docker,sterchelen/docker,coolljt0725/docker,docker/docker,trebonian/docker,diogomonica/docker,michelvocks/docker,AkihiroSuda/docker,KarthikNayak/docker,rremer/moby,cyphar/docker,noironetworks/docker,ibuildthecloud/docker,dperny/docker,moby/moby,gschaetz/moby,justincormack/docker,xuxinkun/docker,shhsu/docker,trebonian/docker,rancher/docker,shhsu/docker,PatrickLang/moby,maxamillion/docker,paralin/docker,qudongfang/docker,allencloud/docker,mtrmac/docker,lixiaobing10051267/docker,nawawi/docker,alfred-landrum/docker,asbjornenge/docker,twaugh/docker,akira-baruah/docker,kojiromike/docker,trebonian/docker,tophj-ibm/docker,tagomoris/docker,mike1729/docker,resin-io/docker,moby/moby,erikh/docker,dsheets/moby,michael-holzheu/docker,jvanz/docker,trebonian/docker,bearstech/moby,stevvooe/docker,srust/docker,yp-engineering/docker,mtesselH/docker,ffoysal/docker,crosbymichael/docker,darrenstahlmsft/docker,haveatry/docker,cyphar/docker,mahak/docker,ibuildthecloud/docker,konstruktoid/docker-upstream,mtesselH/docker,konstruktoid/docker-upstream,cloudflare/docker,xuxinkun/docker,ndeloof/docker,sterchelen/docker