Fix flaky route blinding test.

If the RNG used in the test changes, the sender may be adding fewer blocks as
their random shadow offset to the total CLTV expiry. This should be fine,
except in the case of this test the sender has fallen 30 blocks behind the
receiver, causing the CLTV expiry they set to be too low.

lightning/src/ln/blinded_payment_tests.rs

@@ -510,6 +510,8 @@ fn three_hop_blinded_path_success() {
 	create_announced_chan_between_nodes_with_value(&nodes, 1, 2, 1_000_000, 0);
 	let chan_upd_2_3 = create_announced_chan_between_nodes_with_value(&nodes, 2, 3, 1_000_000, 0).0.contents;
 	let chan_upd_3_4 = create_announced_chan_between_nodes_with_value(&nodes, 3, 4, 1_000_000, 0).0.contents;
+	// Make sure the nodes are on a similar height so nodes[0] sets a valid CLTV expiry.
+	connect_blocks(&nodes[0], nodes[4].best_block_info().1 - nodes[0].best_block_info().1);
 
 	let amt_msat = 5000;
 	let (payment_preimage, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[4], Some(amt_msat), None);