Filter out cloud RoleInstance (#207)

Author: Charles-Gagnon

src/Telemetry/Telemetry.cs

@@ -67,6 +67,7 @@ private void InitializeTelemetry(string productVersion, IConfiguration config)
             try
             {
                 var telemetryConfig = new TelemetryConfiguration(InstrumentationKey);
+                telemetryConfig.TelemetryInitializers.Add(new TelemetryInitializer());
                 this._client = new TelemetryClient(telemetryConfig);
                 this._client.Context.Session.Id = CurrentSessionId;
                 this._client.Context.Device.OperatingSystem = RuntimeInformation.OSDescription;

src/Telemetry/TelemetryInitializer.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using Microsoft.ApplicationInsights.Channel;
+using Microsoft.ApplicationInsights.Extensibility;
+
+namespace Microsoft.Azure.WebJobs.Extensions.Sql.Telemetry
+{
+    public class TelemetryInitializer : ITelemetryInitializer
+    {
+        public void Initialize(ITelemetry telemetry)
+        {
+            // Filter out the Cloud RoleInstance - we don't care about that field and
+            // it can contain information such as the machine and domain name of the client
+            telemetry.Context.Cloud.RoleInstance = "-";
+        }
+    }
+
+}