Don't reset PTO backoff when our address need not be validated

quinn-proto/src/connection/mod.rs

@@ -967,7 +967,9 @@ where
         // Must be called before crypto/pto_count are clobbered
         self.detect_lost_packets(now, space);
 
-        self.pto_count = 0;
+        if self.peer_not_awaiting_address_validation() {
+            self.pto_count = 0;
+        }
 
         // Explicit congestion notification
         if self.path.sending_ecn {