rafthttp: avoid TestStream to use outdated stream

The original test code before fb4b0b5cf075212f79fcdfa58533915a29c0912d
doesn't work because reader side may update the
stream, while writer side writes message to the old stream and fails.

This PR removes unnecessary call to set term, and avoids this problem to
happen on term > 1 in the future.

rafthttp/stream_test.go

@@ -274,11 +274,8 @@ func TestStream(t *testing.T) {
 		h.sw = sw
 
 		picker := mustNewURLPicker(t, []string{srv.URL})
-		sr := startStreamReader(&http.Transport{}, picker, tt.t, types.ID(1), types.ID(2), types.ID(1), newPeerStatus(types.ID(1)), recvc, propc, nil, 1)
+		sr := startStreamReader(&http.Transport{}, picker, tt.t, types.ID(1), types.ID(2), types.ID(1), newPeerStatus(types.ID(1)), recvc, propc, nil, tt.term)
 		defer sr.stop()
-		if tt.t == streamTypeMsgApp {
-			sr.updateMsgAppTerm(tt.term)
-		}
 		// wait for stream to work
 		var writec chan<- raftpb.Message
 		for {