Make test_esplora_syncs more robust

The test generally works and the parts in question *should* never fail.
However, they did, so we give the test server instances some leeway.

lightning-transaction-sync/tests/integration_tests.rs

@@ -32,7 +32,9 @@ fn get_bitcoind() -> &'static BitcoinD {
 				);
 		let mut conf = bitcoind::Conf::default();
 		conf.network = "regtest";
-		BitcoinD::with_conf(bitcoind_exe, &conf).unwrap()
+		let bitcoind = BitcoinD::with_conf(bitcoind_exe, &conf).unwrap();
+		std::thread::sleep(Duration::from_secs(3));
+		bitcoind
 	})
 }
 
@@ -46,7 +48,9 @@ fn get_electrsd() -> &'static ElectrsD {
 		let mut conf = electrsd::Conf::default();
 		conf.http_enabled = true;
 		conf.network = "regtest";
-		ElectrsD::with_conf(electrs_exe, &bitcoind, &conf).unwrap()
+		let electrsd = ElectrsD::with_conf(electrs_exe, &bitcoind, &conf).unwrap();
+		std::thread::sleep(Duration::from_secs(3));
+		electrsd
 	})
 }
 
@@ -60,15 +64,22 @@ fn generate_blocks_and_wait(num: usize) {
 }
 
 fn wait_for_block(min_height: usize) {
-	let mut header = get_electrsd().client.block_headers_subscribe().unwrap();
+	let mut header = match get_electrsd().client.block_headers_subscribe() {
+		Ok(header) => header,
+		Err(_) => {
+			std::thread::sleep(Duration::from_secs(3));
+			get_electrsd().client.block_headers_subscribe().expect("failed to subscribe to block headers")
+		}
+	};
+
 	loop {
 		if header.height >= min_height {
 			break;
 		}
 		header = exponential_backoff_poll(|| {
-			get_electrsd().trigger().unwrap();
-			get_electrsd().client.ping().unwrap();
-			get_electrsd().client.block_headers_pop().unwrap()
+			get_electrsd().trigger().expect("failed to trigger electrsd");
+			get_electrsd().client.ping().expect("failed to ping electrsd");
+			get_electrsd().client.block_headers_pop().expect("failed to pop block header")
 		});
 	}
 }