contrib/raftexample: fix restart path
contrib/raftexample: fix restart path

The ConfChange fix crashes WAL replay because it assumed the node
always exists. Additionally, restart on a single node cluster
would deadlock because it had the wrong raft HardState.

To fix, replay path now goes through the regular raft loop.

Fixes #4474

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