fix #3582 low level client sniffing (#3587)

* fix #3582 #3483 introduced SIMPLE_JSON_TYPEDEF to be defined which caused netstandard and netfx exceptions when deserializing sniff responses, but would light up in different places as well

(cherry picked from commit c49736a)

* update assertion to be 5.x specific

Author: Mpdreamz

src/Elasticsearch.Net/Serialization/SimpleJson.cs

@@ -48,7 +48,6 @@
 
 // original json parsing code from http://techblog.procurios.nl/k/618/news/view/14605/14863/How-do-I-write-my-own-parser-for-JSON.html
 
-#define SIMPLE_JSON_TYPEINFO
 using System;
 using System.CodeDom.Compiler;
 using System.Collections;

src/Tests/Tests/ClientConcepts/LowLevel/SniffOnLowLevelClient.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Linq;
+using Elastic.Xunit.XunitPlumbing;
+using Elasticsearch.Net;
+using FluentAssertions;
+using Tests.Core.Client.Settings;
+using Tests.Core.ManagedElasticsearch.Clusters;
+using Tests.Framework;
+
+namespace Tests.ClientConcepts.LowLevel
+{
+	public class SniffOnLowLevelClient : IClusterFixture<ReadOnlyCluster>
+	{
+		private readonly ReadOnlyCluster _cluster;
+
+		public SniffOnLowLevelClient(ReadOnlyCluster cluster) => _cluster = cluster;
+
+		[I] public void CanSniffUsingJustTheLowLevelClient()
+		{
+			var uri = TestConnectionSettings.CreateUri(_cluster.Nodes.First().Port ?? 9200);
+			var sniffingConnectionPool = new SniffingConnectionPool(new[] { uri });
+			var elasticClient = new ElasticLowLevelClient(new ConnectionConfiguration(sniffingConnectionPool));
+
+			Func<ElasticsearchResponse<DynamicResponse>> act = () => elasticClient.ClusterHealth<DynamicResponse>();
+			act.Invoking(s => s.Invoke()).ShouldNotThrow();
+		}
+
+	}
+}