raft: simplify truncateAndAppend
raft: simplify truncateAndAppend

truncateAndAppend no need the value of 'after' with subbing one

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