etcdserver: remove legacy range/txn
etcdserver: remove legacy range/txn

Needed for 3.0->3.1. Not needed for 3.1->3.2

bdarnell/etcd,xiang90/etcd,dannysauer/etcd,akauppi/etcd,handsomesun/etcd,armstrongli/etcd,joshix/etcd,fanminshi/etcd,mickep76/etcd,sebrandon1/etcd,bdarnell/etcd,visheshnp/etcd,mkumatag/etcd,ajityagaty/etcd,etcd-io/etcd,sinsharat/etcd,rnaveiras/etcd,mickep76/etcd,yudai/etcd,plasticbox/etcd,coreos/etcd,rnaveiras/etcd,gyuho/etcd,lumjjb/etcd,whuwxl/etcd,bluebreezecf/etcd,a-robinson/etcd,jlamillan/etcd,glevand/coreos--etcd,etcd-io/etcd,visheshnp/etcd,li-ang/etcd,YuleiXiao/etcd,vimalk78/etcd,heyitsanthony/etcd,mkumatag/etcd,sinsharat/etcd,coreos/etcd,whuwxl/etcd,dannysauer/etcd,tguangch/etcd,lorneli/etcd,mqliang/etcd,li-ang/etcd,sebrandon1/etcd,bluebreezecf/etcd,mqliang/etcd,cockroachdb/etcd,cockroachdb/etcd,a-robinson/etcd,rnaveiras/etcd,tguangch/etcd,joshix/etcd,heyitsanthony/etcd,vimalk78/etcd,gyuho/etcd,jlamillan/etcd,mqliang/etcd,yudai/etcd,plasticbox/etcd,fanminshi/etcd,YuleiXiao/etcd,ajityagaty/etcd,glevand/coreos--etcd,xiang90/etcd,mkumatag/etcd,lorneli/etcd,armstrongli/etcd,ajityagaty/etcd,akauppi/etcd,handsomesun/etcd,etcd-io/etcd,lumjjb/etcd