etcdserver: move 'EtcdServer.send' to raft.go

Clear 'TODO'

etcdserver/server_test.go

@@ -971,14 +971,15 @@ func TestConcurrentApplyAndSnapshotV3(t *testing.T) {
 			DataDir: testdir,
 		},
 		r: raftNode{
+			isIDRemoved: func(id uint64) bool { return cl.IsIDRemoved(types.ID(id)) },
 			Node:        n,
 			transport:   tr,
 			storage:     mockstorage.NewStorageRecorder(testdir),
 			raftStorage: rs,
+			msgSnapC:    make(chan raftpb.Message, maxInFlightMsgSnap),
 		},
-		store:    st,
-		cluster:  cl,
-		msgSnapC: make(chan raftpb.Message, maxInFlightMsgSnap),
+		store:   st,
+		cluster: cl,
 	}
 	s.applyV2 = &applierV2store{store: s.store, cluster: s.cluster}