Add testcase for build arg without value
Add testcase for build arg without value

Signed-off-by: Tonis Tiigi <c2470c48b2d3312d61f94f18d3a1cd113d1915ad@gmail.com>

amatsus/docker,kolyshkin/moby,lixiaobing10051267/docker,justincormack/docker,tophj-ibm/docker,jthelin/docker,paralin/docker,yummypeng/docker,dperny/docker,flavio/docker,dmcgowan/docker,naveed-jamil-tenpearls/moby,estesp/docker,prertik/docker,AkihiroSuda/docker,mahak/docker,estesp/docker,madhanrm/docker,JMesser81/docker,gschaetz/moby,flavio/docker,shishir-a412ed/docker,Ramzec/docker,Syntaxide/docker,coreos/docker,shhsu/docker,pramodhkp/moby,mike1729/docker,fcrisciani/docker,liaoqingwei/docker,duglin/docker,dperny/docker,tianon/docker,diogomonica/docker,tianon/docker,dsheets/moby,bonczj/moby-json-file-logger,ibuildthecloud/docker,ndeloof/docker,cpuguy83/docker,thtanaka/docker,whuwxl/docker,rhatdan/docker,yummypeng/docker,ColinHebert/docker,AkihiroSuda/docker,prertik/docker,thaJeztah/docker,mahak/docker,Mokolea/docker,catinthesky/docker,rancher/docker,darrenstahlmsft/docker,charleszheng44/moby,allencloud/docker,coolljt0725/docker,yummypeng/docker,rancher/docker,nalind/docker,yongtang/docker,naveed-jamil-tenpearls/moby,ripcurld0/moby,konstruktoid/docker-upstream,ibuildthecloud/docker,shishir-a412ed/docker,ffoysal/docker,alfred-landrum/docker,mkumatag/docker,KarthikNayak/docker,jimjag/docker,nalind/docker,estesp/docker,charleszheng44/moby,JMesser81/docker,moby/moby,flavio/docker,dmcgowan/docker,x1022as/docker,JMesser81/docker,PatrickLang/moby,whuwxl/docker,cyphar/docker,mixja/docker,tophj-ibm/moby,unclejack/docker,yasiramin10p/moby,laijs/moby,mtesselH/docker,flavio/docker,amatsus/docker,mtesselH/docker,moul/docker,ibuildthecloud/docker,laijs/docker,coolljt0725/docker,moby/moby,jameszhan/docker,sterchelen/docker,resin-io/docker,dccurtis/docker,cyphar/docker,prertik/docker,ffoysal/docker,YuPengZTE/docker,allencloud/docker,yongtang/docker,naveed-jamil-tenpearls/moby,johnstep/moby-moby,jameszhan/docker,pramodhkp/moby,ColinHebert/docker,kojiromike/docker,crosbymichael/docker,x1022as/docker,moby/moby,duglin/docker,x1022as/docker,erikh/docker,lixiaobing10051267/docker,sdurrheimer/docker,PatrickLang/moby,crosbymichael/docker,gjaskiewicz/moby,thaJeztah/docker,konstruktoid/docker-1,mtesselH/docker,vdemeester/docker,srust/docker,liaoqingwei/docker,alfred-landrum/docker,alfred-landrum/docker,tophj-ibm/docker,kolyshkin/docker,darrenstahlmsft/moby,liaoqingwei/docker,ndeloof/docker,mikebrow/docker,mkumatag/docker,laijs/moby,jvanz/docker,cpuguy83/docker,resin-io/docker,jlhawn/docker,moul/docker,vdemeester/docker,jwhonce/docker,shhsu/docker,miminar/docker,sarnautov/moby,moypray/docker,tmp6154/docker,laijs/docker,kolyshkin/docker,justincormack/docker,mike1729/docker,dsheets/moby,tklauser/docker,cpuguy83/docker,paralin/docker,gjaskiewicz/moby,yosifkit/docker,raja-sami-10p/moby,miminar/docker,ndeloof/docker,jimjag/docker,YuPengZTE/docker,vdemeester/docker,lixiaobing1/docker,johnstep/moby-moby,pradipd/moby,michael-holzheu/docker,trebonian/docker,kolyshkin/moby,nawawi/docker,raja-sami-10p/moby,haveatry/docker,justincormack/docker,lixiaobing1/docker,akira-baruah/docker,yosifkit/docker,konstruktoid/docker-1,dims/docker,rhatdan/docker,lixiaobing1/docker,Syntaxide/docker,tmp6154/docker,raja-sami-10p/moby,bearstech/moby,kencochrane/docker,michael-holzheu/docker,dccurtis/docker,shishir-a412ed/docker,darrenstahlmsft/docker,Ramzec/docker,djs55/docker,michael-holzheu/docker,PatrickLang/moby,tklauser/docker,ripcurld0/moby,laijs/docker,Ramzec/docker,rremer/moby,Mokolea/docker,fcrisciani/docker,haveatry/docker,jvanz/docker,maxamillion/docker,kencochrane/docker,rremer/moby,thaJeztah/docker,darrenstahlmsft/moby,scotttlin/docker,akira-baruah/docker,bonczj/moby-json-file-logger,djs55/docker,miminar/docker,mixja/docker,trebonian/docker,yosifkit/docker,kojiromike/docker,bearstech/moby,pramodhkp/moby,catinthesky/docker,whuwxl/docker,moypray/docker,scotttlin/docker,ibuildthecloud/docker,tklauser/docker,gjaskiewicz/moby,docker/docker,rremer/moby,charleszheng44/moby,paralin/docker,hqhq/moby,Ramzec/docker,catinthesky/docker,mikebrow/docker,imkin/moby,kencochrane/docker,POLJM242/docker,sarnautov/moby,KingEmet/docker,jimjag/docker,gschaetz/moby,jwhonce/docker,noironetworks/docker,hqhq/moby,unclejack/docker,jthelin/docker,moul/docker,tonistiigi/docker,nawawi/docker,lixiaobing10051267/docker,jwhonce/docker,erikh/docker,madhanrm/docker,diogomonica/docker,YuPengZTE/docker,moul/docker,Mokolea/docker,tophj-ibm/docker,kojiromike/docker,scotttlin/docker,jvanz/docker,yasiramin10p/moby,thtanaka/docker,yasiramin10p/moby,ffoysal/docker,bearstech/moby,cyphar/docker,hqhq/moby,maxamillion/docker,konstruktoid/docker-upstream,trebonian/docker,kolyshkin/moby,danyalKhaliq10p/moby,KarthikNayak/docker,mstanleyjones/docker,Syntaxide/docker,mike1729/docker,coolljt0725/docker,konstruktoid/docker-upstream,tophj-ibm/moby,erikh/docker,nawawi/docker,darrenstahlmsft/moby,mahak/docker,madhanrm/docker,sdurrheimer/docker,gnailuy/docker,dmcgowan/docker,imkin/moby,POLJM242/docker,KarthikNayak/docker,KingEmet/docker,paralin/docker,haveatry/docker,allencloud/docker,pradipd/moby,noironetworks/docker,tmp6154/docker,danyalKhaliq10p/moby,Mokolea/docker,dccurtis/docker,trebonian/docker,moypray/docker,konstruktoid/docker-1,shhsu/docker,tophj-ibm/moby,moby/moby,gnailuy/docker,mahak/docker,coreos/docker,ibuildthecloud/docker,SvenDowideit/docker,darrenstahlmsft/docker,thaJeztah/docker,johnstep/moby-moby,rancher/docker,tonistiigi/docker,sdurrheimer/docker,mstanleyjones/docker,docker/docker,yongtang/docker,imkin/moby,amatsus/docker,fcrisciani/docker,dsheets/moby,nalind/docker,duglin/docker,gschaetz/moby,crosbymichael/docker,jameszhan/docker,mkumatag/docker,gnailuy/docker,jimjag/docker,sarnautov/moby,maxamillion/docker,jlhawn/docker,srust/docker,diogomonica/docker,mstanleyjones/docker,noironetworks/docker,SvenDowideit/docker,bearstech/moby,yosifkit/docker,ColinHebert/docker,docker/docker,pradipd/moby,ripcurld0/moby,mixja/docker,KingEmet/docker,dperny/docker,SvenDowideit/docker,rhatdan/docker,gnailuy/docker,resin-io/docker,coreos/docker,laijs/moby,nawawi/docker,AkihiroSuda/docker,tonistiigi/docker,nalind/docker,konstruktoid/docker-upstream,sterchelen/docker,sterchelen/docker,cpuguy83/docker,srust/docker,dims/docker,bonczj/moby-json-file-logger,mikebrow/docker,AkihiroSuda/docker,unclejack/docker,dims/docker,danyalKhaliq10p/moby,djs55/docker,thtanaka/docker,jlhawn/docker