Remove some unused code and fix flaky test (Azure#18933)

Author: JoshLove-msft

sdk/servicebus/Azure.Messaging.ServiceBus/src/Client/ServiceBusClient.cs

@@ -647,24 +647,6 @@ public virtual ServiceBusSessionProcessor CreateSessionProcessor(
                 options: options ?? new ServiceBusSessionProcessorOptions());
         }
 
-        /// <summary>
-        /// The <see cref="ServiceBusRuleManager"/> is used to manage the rules for a subscription.
-        /// </summary>
-        ///
-        /// <param name="topicName">The topic to create a <see cref="ServiceBusRuleManager"/> for.</param>
-        /// <param name="subscriptionName">The subscription specific to the specified topic to create
-        /// a <see cref="ServiceBusRuleManager"/> for.</param>
-        ///
-        /// <returns>A <see cref="ServiceBusRuleManager"/> scoped to the specified subscription and topic.</returns>
-        internal ServiceBusRuleManager CreateRuleManager(string topicName, string subscriptionName)
-        {
-            ValidateEntityName(topicName);
-
-            return new ServiceBusRuleManager(
-                connection: Connection,
-                subscriptionPath: EntityNameFormatter.FormatSubscriptionPath(topicName, subscriptionName));
-        }
-
         /// <summary>
         /// Validates that the specified entity name matches the entity path in the Connection,
         /// if an entity path is specified in the connection.

sdk/servicebus/Azure.Messaging.ServiceBus/src/RuleManager/ServiceBusRuleManager.cs

@@ -1202,7 +1202,9 @@ async Task ProcessMessage(ProcessSessionMessageEventArgs args)
                     {
                         var message = args.Message;
                         sessions.TryRemove(message.SessionId, out bool _);
-                        await Task.Delay(lockDuration.Add(TimeSpan.FromSeconds(10)));
+                        // wait 3x lockduration since to avoid the case where
+                        // lock is renewed at the very end of the lock duration delay
+                        await Task.Delay(lockDuration.Add(lockDuration).Add(lockDuration));
                         await args.CompleteMessageAsync(message);
 
                         Assert.IsTrue(sessionId.Contains(message.SessionId));