Don't generate redundant PaymentFailed events on abandon

Author: valentinewallace

lightning/src/ln/outbound_payment.rs

@@ -1189,7 +1189,7 @@ impl OutboundPayments {
 	) {
 		let mut outbounds = self.pending_outbound_payments.lock().unwrap();
 		if let hash_map::Entry::Occupied(mut payment) = outbounds.entry(payment_id) {
-			if let Ok(()) = payment.get_mut().mark_abandoned() {
+			if !payment.get().abandoned() && payment.get_mut().mark_abandoned().is_ok() {
 				if payment.get().remaining_parts() == 0 {
 					pending_events.lock().unwrap().push(events::Event::PaymentFailed {
 						payment_id,