etcdctl/command: print more details about ErrNoEndpoint
etcdctl/command: print more details about ErrNoEndpoint

This commit prints more details if getting ErrNoEndpoint when sync with
cluster. This helps users to know what happens.

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