Documentation: docker pull latest etcd from quay
Documentation: docker pull latest etcd from quay

As pointed out at https://github.com/coreos/etcd/issues/3843, Docker guide uses
outdated version of etcd. This docker commands will pull from the latest
releases.

bdarnell/etcd,insequent/etcd,plasticbox/etcd,endocode/etcd,rnaveiras/etcd,ravigadde/etcd,tamird/etcd,CrazyJvm/etcd,ravigadde/etcd,Timer/etcd,bdarnell/etcd,fasaxc/etcd,cchamplin/etcd,westhood/etcd,akauppi/etcd,mkumatag/etcd,sebrandon1/etcd,zaphod-concur/etcd,raoofm/etcd,endocode/etcd,sinsharat/etcd,luxas/etcd,heyitsanthony/etcd,insequent/etcd,tamird/etcd,purpleidea/etcd,chipironcin/etcd,achanda/etcd,etcd-io/etcd,rnaveiras/etcd,fanminshi/etcd,glevand/coreos--etcd,etcd-io/etcd,dnaeon/etcd,qqsun8819/etcd,dnaeon/etcd,qqsun8819/etcd,handsomesun/etcd,lorneli/etcd,oscarrr110/etcd,dannysauer/etcd,yudai/etcd,achanda/etcd,glycerine/etcd,coreos/etcd,cockroachdb/etcd,armstrongli/etcd,nekto0n/etcd,fasaxc/etcd,ajityagaty/etcd,coreos/etcd,joshix/etcd,lumjjb/etcd,HideoYamauchi/etcd,hongchaodeng/etcd,shawnps/etcd,lumjjb/etcd,CrazyJvm/etcd,li-ang/etcd,sofuture/etcd,zaphod-concur/etcd,whuwxl/etcd,xiang90/etcd,wantonsolutions/dinv-etcd,gyuho/etcd,visheshnp/etcd,ktateish/etcd,yudai/etcd,shawnps/etcd,OyTao/etcd_learning,whuwxl/etcd,fanminshi/etcd,swingbach/etcd,siddontang/etcd,vimalk78/etcd,a-robinson/etcd,StorReduce/etcd,akauppi/etcd,sofuture/etcd,luxas/etcd,rchicoli/etcd,mkumatag/etcd,bluebreezecf/etcd,OyTao/etcd_learning,HideoYamauchi/etcd,swingbach/etcd,dannysauer/etcd,linuxcer/etcd,plasticbox/etcd,wantonsolutions/dinv-etcd,ktateish/etcd,etcd-io/etcd,purpleidea/etcd,mqliang/etcd,rnaveiras/etcd,vimalk78/etcd,raoofm/etcd,ajityagaty/etcd,heyitsanthony/etcd,mickep76/etcd,sebrandon1/etcd,sayden/etcd,oscarrr110/etcd,gyuho/etcd,sinsharat/etcd,ajityagaty/etcd,lorneli/etcd,jlamillan/etcd,hongchaodeng/etcd,chipironcin/etcd,YuleiXiao/etcd,mkumatag/etcd,mqliang/etcd,linuxcer/etcd,Timer/etcd,glevand/coreos--etcd,cchamplin/etcd,siddontang/etcd,xiang90/etcd,westhood/etcd,nekto0n/etcd,glycerine/etcd,StorReduce/etcd,jonboulle/etcd,handsomesun/etcd,YuleiXiao/etcd,jlamillan/etcd,a-robinson/etcd,sayden/etcd,jonboulle/etcd,joshix/etcd,tguangch/etcd,tguangch/etcd,mickep76/etcd,armstrongli/etcd,fasaxc/etcd,mqliang/etcd,rchicoli/etcd,cockroachdb/etcd,visheshnp/etcd,bluebreezecf/etcd,wantonsolutions/dinv-etcd,li-ang/etcd