etcdserver: use Counter for proposals_failed_total
etcdserver: use Counter for proposals_failed_total

It only ever goes up.

glevand/coreos--etcd,akauppi/etcd,qqsun8819/etcd,ajityagaty/etcd,whuwxl/etcd,glycerine/etcd,lorneli/etcd,vimalk78/etcd,rchicoli/etcd,endocode/etcd,mkumatag/etcd,rchicoli/etcd,handsomesun/etcd,ravigadde/etcd,nekto0n/etcd,joshix/etcd,bdarnell/etcd,joshix/etcd,luxas/etcd,sinsharat/etcd,purpleidea/etcd,armstrongli/etcd,YuleiXiao/etcd,etcd-io/etcd,visheshnp/etcd,tguangch/etcd,purpleidea/etcd,cockroachdb/etcd,mickep76/etcd,insequent/etcd,hongchaodeng/etcd,OyTao/etcd_learning,coreos/etcd,fanminshi/etcd,mkumatag/etcd,cockroachdb/etcd,rnaveiras/etcd,etcd-io/etcd,rnaveiras/etcd,glycerine/etcd,mkumatag/etcd,tguangch/etcd,akauppi/etcd,sebrandon1/etcd,rnaveiras/etcd,xiang90/etcd,dannysauer/etcd,lorneli/etcd,OyTao/etcd_learning,luxas/etcd,jonboulle/etcd,lumjjb/etcd,mqliang/etcd,heyitsanthony/etcd,xiang90/etcd,plasticbox/etcd,gyuho/etcd,visheshnp/etcd,ktateish/etcd,ajityagaty/etcd,zaphod-concur/etcd,CrazyJvm/etcd,insequent/etcd,mickep76/etcd,linuxcer/etcd,endocode/etcd,linuxcer/etcd,plasticbox/etcd,coreos/etcd,yudai/etcd,fanminshi/etcd,yudai/etcd,jonboulle/etcd,YuleiXiao/etcd,a-robinson/etcd,CrazyJvm/etcd,bluebreezecf/etcd,a-robinson/etcd,zaphod-concur/etcd,mqliang/etcd,qqsun8819/etcd,dannysauer/etcd,handsomesun/etcd,sinsharat/etcd,bdarnell/etcd,armstrongli/etcd,gyuho/etcd,hongchaodeng/etcd,li-ang/etcd,ajityagaty/etcd,ktateish/etcd,bluebreezecf/etcd,lumjjb/etcd,nekto0n/etcd,whuwxl/etcd,ravigadde/etcd,jlamillan/etcd,etcd-io/etcd,sebrandon1/etcd,vimalk78/etcd,heyitsanthony/etcd,mqliang/etcd,li-ang/etcd,glevand/coreos--etcd,jlamillan/etcd