CSHARP-315: add support for reading tags from isMaster result.

Author: craiggwilson

Driver/Core/CommandResults/IsMasterResult.cs

@@ -187,6 +187,27 @@ public string ReplicaSetName
             }
         }
 
+        /// <summary>
+        /// Gets the tags.
+        /// </summary>
+        public ReplicaSetTagSet Tags
+        {
+            get
+            {
+                var tagSet = new ReplicaSetTagSet();
+                if (Response.Contains("tags"))
+                {
+                    var tags = Response["tags"].AsBsonDocument;
+                    foreach (var tag in tags)
+                    {
+                        tagSet.Add(tag.Name, tag.Value.ToString());
+                    }
+                }
+
+                return tagSet;
+            }
+        }
+
         // private methods
         private IEnumerable<MongoServerAddress> GetInstanceAddressesFromNamedResponseElement(string elementName)
         {

Driver/Core/MongoServerInstance.cs

@@ -521,9 +521,8 @@ private void LookupServerInformation(MongoConnection connection)
                 MongoServerInstanceType instanceType = MongoServerInstanceType.StandAlone;
                 if (isMasterResult.ReplicaSetName != null)
                 {
-                    var tagSet = new ReplicaSetTagSet();
                     var peers = isMasterResult.Hosts.Concat(isMasterResult.Passives).Concat(isMasterResult.Arbiters).ToList();
-                    replicaSetInformation = new ReplicaSetInformation(isMasterResult.ReplicaSetName, isMasterResult.Primary, peers, tagSet);
+                    replicaSetInformation = new ReplicaSetInformation(isMasterResult.ReplicaSetName, isMasterResult.Primary, peers, isMasterResult.Tags);
                     instanceType = MongoServerInstanceType.ReplicaSetMember;
                 }
                 else if (isMasterResult.Message != null && isMasterResult.Message == "isdbgrid")