Use consistent hostname in display and processor

Previously, the hostname written to the console and the hostname used
for the ChangeFeedProcessor were different. The console was the string
"hostName" with a timestamp. The ChangeFeedProcessor used a GUID.

Now, both use a value based on the current machine's name with a
timestamp, like "MY-MACHINE@636693244993023673".

samples/code-samples/ChangeFeedProcessorV2/Program.cs

@@ -41,6 +41,8 @@ namespace ChangeFeedProcessor
         private string leaseCollectionName = ConfigurationManager.AppSettings["leaseCollectionName"];
         private int leaseThroughput = int.Parse(ConfigurationManager.AppSettings["leaseThroughput"]);
 
+        private static string hostName = Environment.MachineName + "@" + DateTime.Now.Ticks.ToString();
+
         private readonly CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
 
         /// <summary>
@@ -50,8 +52,6 @@ namespace ChangeFeedProcessor
         ///
         public static void Main(string[] args)
         {
-            string hostName = "HostName " + DateTime.Now.Ticks.ToString();
-
             if (args.Length == 1)
             {
                 hostName = args[0];
@@ -106,8 +106,6 @@ namespace ChangeFeedProcessor
 
         public async Task RunChangeFeedHostAsync()
         {
-            string hostName = Guid.NewGuid().ToString();
-
             // monitored collection info
             DocumentCollectionInfo documentCollectionInfo = new DocumentCollectionInfo
             {
@@ -117,7 +115,6 @@ namespace ChangeFeedProcessor
                 CollectionName = this.monitoredCollectionName
             };
 
-
             DocumentCollectionInfo leaseCollectionInfo = new DocumentCollectionInfo
             {
                 Uri = new Uri(this.leaseUri),
@@ -148,7 +145,6 @@ namespace ChangeFeedProcessor
             await result.StopAsync();
         }
 
-
         /// <summary>
         /// Checks whether a collections exists. Creates a new collection if
         /// the collection does not exist.