Fixing twin tests for connectivity (Azure#2631)

We are seeing a bug in Connectivity Twin Tests. 

When we start the tests, we do a cleanup - where we grab the current twin, set its properties to null, and send an UpdateReportedProperties call. Due to how the SDK works, this will automatically subscribe us for receiving DesiredPropertiesUpdates (DPU). But then we wait for 2 minutes due to the testStartDelay. After that, we set the callback for receiving DPUs.

The issue is that if we receive a DPU during the testStartDelay, the callback won't be set, and we will do nothing. 

So this PR moves the callback up before the testStartDelay, so that we are ready to receive even during the waiting period. 

It also removes the cleanup because it is unnecessary now that we are using a fresh device every time.

test/modules/TwinTester/DesiredPropertyReceiver.cs

@@ -22,6 +22,7 @@ public DesiredPropertyReceiver(ModuleClient moduleClient, ITwinTestResultHandler
 
         public Task UpdateAsync()
         {
+            Logger.LogInformation("Setting desired property update callback");
             return this.moduleClient.SetDesiredPropertyUpdateCallbackAsync(this.OnDesiredPropertyUpdateAsync, null);
         }
 

test/modules/TwinTester/TwinCloudOperationsInitializer.cs

@@ -30,13 +30,9 @@ public static async Task<TwinCloudOperationsInitializer> CreateAsync(RegistryMan
                 TwinState initializedState;
                 Twin twin = await registryManager.GetTwinAsync(Settings.Current.DeviceId, Settings.Current.TargetModuleId);
 
-                // reset desired properties
-                twin.Properties.Desired = null;
-                Twin desiredPropertyResetTwin = await registryManager.ReplaceTwinAsync(Settings.Current.DeviceId, Settings.Current.TargetModuleId, twin, twin.ETag);
+                initializedState = new TwinState { TwinETag = twin.ETag };
 
-                initializedState = new TwinState { TwinETag = desiredPropertyResetTwin.ETag };
-
-                Logger.LogInformation($"Start state of module twin: {JsonConvert.SerializeObject(desiredPropertyResetTwin, Formatting.Indented)}");
+                Logger.LogInformation($"Start state of module twin: {JsonConvert.SerializeObject(twin, Formatting.Indented)}");
                 return new TwinCloudOperationsInitializer(registryManager, resultHandler, initializedState);
             }
             catch (Exception e)

test/modules/TwinTester/TwinEdgeOperationsInitializer.cs

@@ -28,29 +28,18 @@ class TwinEdgeOperationsInitializer : ITwinTestInitializer
             this.desiredPropertiesReceiver = new DesiredPropertyReceiver(moduleClient, reporter);
         }
 
-        public static async Task<TwinEdgeOperationsInitializer> CreateAsync(RegistryManager registryManager, ModuleClient moduleClient, ITwinTestResultHandler reporter)
+        public static Task<TwinEdgeOperationsInitializer> CreateAsync(RegistryManager registryManager, ModuleClient moduleClient, ITwinTestResultHandler reporter)
         {
-            try
-            {
-                Twin twin = await registryManager.GetTwinAsync(Settings.Current.DeviceId, Settings.Current.TargetModuleId);
-
-                // reset reported properties
-                await TwinTesterUtil.ResetTwinReportedPropertiesAsync(moduleClient, twin);
-                return new TwinEdgeOperationsInitializer(registryManager, moduleClient, reporter, 0);
-            }
-            catch (Exception e)
-            {
-                throw new Exception($"Shutting down module. Initialization failure: {e}");
-            }
+            return Task.FromResult(new TwinEdgeOperationsInitializer(registryManager, moduleClient, reporter, 0));
         }
 
         public async Task StartAsync(CancellationToken cancellationToken)
         {
+            await this.desiredPropertiesReceiver.UpdateAsync();
             Logger.LogInformation($"Waiting for {Settings.Current.TestStartDelay} based on TestStartDelay setting before starting.");
             await Task.Delay(Settings.Current.TestStartDelay, cancellationToken);
             await this.LogEdgeDeviceTwin();
             this.periodicUpdate = new PeriodicTask(this.UpdateAsync, Settings.Current.TwinUpdateFrequency, Settings.Current.TwinUpdateFrequency, Logger, "TwinReportedPropertiesUpdate");
-            await this.desiredPropertiesReceiver.UpdateAsync();
         }
 
         async Task LogEdgeDeviceTwin()