scripts/build-docker: build docker in image-docker dir
scripts/build-docker: build docker in image-docker dir

The docker build command will use whatever directory contains the
Dockerfile as the build context (including all of its subdirectories).
And the <src> path of ADD must be inside the context of the build.
So change it to build in a specific directory for clean and fast.

fanminshi/etcd,chipironcin/etcd,pauldallen/etcd,glevand/coreos--etcd,wantonsolutions/dinv-etcd,CrazyJvm/etcd,asim/etcd,jeremyeder/etcd,qqsun8819/etcd,jeremyeder/etcd,fgbreel/etcd,armstrongli/etcd,xdlinear/etcd,tamird/etcd,sinsharat/etcd,etcd-io/etcd,mike-lerch/etcd,giantswarm/etcd,jchauncey/etcd,OyTao/etcd_learning,kkaneda/etcd,westhood/etcd,dnaeon/etcd,rnaveiras/etcd,gyuho/etcd,sebrandon1/etcd,siddontang/etcd,hongbinz/etcd,wantonsolutions/dinv-etcd,yichengq/etcd,a-robinson/etcd,jonboulle/etcd,visheshnp/etcd,lorneli/etcd,beni55/etcd,shawnps/etcd,asim/etcd,li-ang/etcd,lumjjb/etcd,mqliang/etcd,ktateish/etcd,jonboulle/etcd,ravigadde/etcd,mickep76/etcd,dannysauer/etcd,cchamplin/etcd,fasaxc/etcd,jlamillan/etcd,cchamplin/etcd,nekto0n/etcd,sofuture/etcd,sayden/etcd,oscarrr110/etcd,handsomesun/etcd,xychu/etcd,Timer/etcd,beni55/etcd,yudai/etcd,gyuho/etcd,hongbinz/etcd,HideoYamauchi/etcd,bdarnell/etcd,whuwxl/etcd,westhood/etcd,giantswarm/etcd,YuleiXiao/etcd,ajityagaty/etcd,msanterre/etcd,insequent/etcd,luxas/etcd,hroyrh/etcd,Timer/etcd,raoofm/etcd,lumjjb/etcd,swingbach/etcd,whuwxl/etcd,endocode/etcd,joshix/etcd,onlyjob/etcd,TheHippo/etcd,iamqizhao/etcd,StorReduce/etcd,zaphod-concur/etcd,vimalk78/etcd,hongchaodeng/etcd,linuxcer/etcd,glevand/coreos--etcd,improbable-io/etcd,etcd-io/etcd,linuxcer/etcd,rnaveiras/etcd,plasticbox/etcd,siddontang/etcd,StorReduce/etcd,swingbach/etcd,qqsun8819/etcd,shawnps/etcd,onlyjob/etcd,achanda/etcd,mickep76/etcd,OyTao/etcd_learning,coreos/etcd,jlamillan/etcd,sayden/etcd,rchicoli/etcd,gae123/etcd,mike-lerch/etcd,fasaxc/etcd,chipironcin/etcd,rnaveiras/etcd,buaazp/etcd,glycerine/etcd,sofuture/etcd,mkumatag/etcd,achanda/etcd,vimalk78/etcd,Winslett/etcd,combk8s/etcd,xiang90/etcd,Eagle-X/etcd,mqliang/etcd,kkaneda/etcd,akauppi/etcd,jchauncey/etcd,xiang90/etcd,bluebreezecf/etcd,gouyang/etcd,YuleiXiao/etcd,wowsoso/etcd,endocode/etcd,delkyd/etcd,yichengq/etcd,fgbreel/etcd,sinsharat/etcd,mkumatag/etcd,oscarrr110/etcd,wowsoso/etcd,handsomesun/etcd,purpleidea/etcd,tguangch/etcd,yudai/etcd,dannysauer/etcd,glycerine/etcd,pauldallen/etcd,xychu/etcd,joshix/etcd,bluebreezecf/etcd,ajityagaty/etcd,heyitsanthony/etcd,CrazyJvm/etcd,tamird/etcd,lorneli/etcd,fasaxc/etcd,iamqizhao/etcd,heyitsanthony/etcd,Winslett/etcd,armstrongli/etcd,visheshnp/etcd,bdarnell/etcd,rchicoli/etcd,coreos/etcd,mqliang/etcd,buaazp/etcd,raoofm/etcd,zaphod-concur/etcd,ravigadde/etcd,mkumatag/etcd,delkyd/etcd,ajityagaty/etcd,combk8s/etcd,TheHippo/etcd,cockroachdb/etcd,sebrandon1/etcd,akauppi/etcd,gouyang/etcd,gae123/etcd,msanterre/etcd,cockroachdb/etcd,improbable-io/etcd,etcd-io/etcd,insequent/etcd,ktateish/etcd,HideoYamauchi/etcd,fanminshi/etcd,xdlinear/etcd,luxas/etcd,hongchaodeng/etcd,wantonsolutions/dinv-etcd,li-ang/etcd,hroyrh/etcd,purpleidea/etcd,dnaeon/etcd,nekto0n/etcd,a-robinson/etcd,plasticbox/etcd,Eagle-X/etcd,tguangch/etcd