Fix wait_for_tx exponential backoff

Backoff wasn't actually working and polling would happen without any
delay at all.

Author: joostjager

tests/common/mod.rs

@@ -437,16 +437,10 @@ pub(crate) fn wait_for_block<E: ElectrumApi>(electrs: &E, min_height: usize) {
 }
 
 pub(crate) fn wait_for_tx<E: ElectrumApi>(electrs: &E, txid: Txid) {
-	let mut tx_res = electrs.transaction_get(&txid);
-	loop {
-		if tx_res.is_ok() {
-			break;
-		}
-		tx_res = exponential_backoff_poll(|| {
-			electrs.ping().unwrap();
-			Some(electrs.transaction_get(&txid))
-		});
-	}
+	exponential_backoff_poll(|| {
+		electrs.ping().unwrap();
+		electrs.transaction_get(&txid).ok()
+	});
 }
 
 pub(crate) fn wait_for_outpoint_spend<E: ElectrumApi>(electrs: &E, outpoint: OutPoint) {