Reduced strictness of rate limiter, to allow two additional file list requests (15 and 30 seconds after initial attempt)

This should help catch any remaining chunks that were unable to be fetched in the first attempt due to network failures, bad peers, etc.

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataFileListManager.java

@@ -103,6 +103,18 @@ public class ArbitraryDataFileListManager {
         }
 
         long timeSinceLastAttempt = NTP.getTime() - lastAttemptTimestamp;
+
+        // Allow a second attempt after 15 seconds, and another after 30 seconds
+        if (timeSinceLastAttempt > 15 * 1000L) {
+            // We haven't tried for at least 15 seconds
+
+            if (networkBroadcastCount < 3) {
+                // We've made less than 3 total attempts
+                return true;
+            }
+        }
+
+        // Then allow another 5 attempts, each 5 minutes apart
         if (timeSinceLastAttempt > 5 * 60 * 1000L) {
             // We haven't tried for at least 5 minutes
 
@@ -112,6 +124,7 @@ public class ArbitraryDataFileListManager {
             }
         }
 
+        // From then on, only try once every 24 hours, to reduce network spam
         if (timeSinceLastAttempt > 24 * 60 * 60 * 1000L) {
             // We haven't tried for at least 24 hours
             return true;