Further removal of preserveAsyncOrder

This parses the option (so it remains valid), but always returns false in all cases since that's the actual behavior. Also removes outputting it in .ToString().

StackExchange.Redis.Tests/Issues/Issue791.cs

@@ -10,35 +10,26 @@ public class Issue791 : TestBase
         [Fact]
         public void PreserveAsyncOrderImplicitValue_ParsedFromConnectionString()
         {
+            // We only care that it parses successfully while deprecated
             var options = ConfigurationOptions.Parse("preserveAsyncOrder=true");
-#pragma warning disable CS0618
-            Assert.True(options.PreserveAsyncOrder);
-#pragma warning restore CS0618
-            Assert.Equal("preserveAsyncOrder=True", options.ToString());
+            Assert.Equal("", options.ToString());
 
+            // We only care that it parses successfully while deprecated
             options = ConfigurationOptions.Parse("preserveAsyncOrder=false");
-#pragma warning disable CS0618
-            Assert.False(options.PreserveAsyncOrder);
-#pragma warning restore CS0618
-            Assert.Equal("preserveAsyncOrder=False", options.ToString());
+            Assert.Equal("", options.ToString());
         }
 
         [Fact]
         public void DefaultValue_IsTrue()
         {
             var options = ConfigurationOptions.Parse("ssl=true");
-#pragma warning disable CS0618
-            Assert.True(options.PreserveAsyncOrder);
-#pragma warning restore CS0618
         }
 
         [Fact]
         public void PreserveAsyncOrder_SetConnectionMultiplexerProperty()
         {
+            // We only care that it parses successfully while deprecated
             var multiplexer = ConnectionMultiplexer.Connect(TestConfig.Current.MasterServerAndPort + ",preserveAsyncOrder=false");
-#pragma warning disable CS0618
-            Assert.False(multiplexer.PreserveAsyncOrder);
-#pragma warning restore CS0618
         }
     }
 }

StackExchange.Redis/StackExchange/Redis/ConfigurationOptions.cs

@@ -124,7 +124,7 @@ public static string TryNormalize(string value)
             }
         }
 
-        private bool? allowAdmin, abortOnConnectFail, highPrioritySocketThreads, resolveDns, ssl, preserveAsyncOrder;
+        private bool? allowAdmin, abortOnConnectFail, highPrioritySocketThreads, resolveDns, ssl;
 
         private string tieBreaker, sslHost, configChannel;
 
@@ -261,8 +261,8 @@ public int ConnectTimeout
         [Obsolete("Not supported; if you require ordered pub/sub, please see " + nameof(ChannelMessageQueue), false)]
         public bool PreserveAsyncOrder
         {
-            get { return preserveAsyncOrder.GetValueOrDefault(true); }
-            set { preserveAsyncOrder = value; }
+            get { return false; }
+            set { }
         }
 
         /// <summary>
@@ -400,7 +400,6 @@ public ConfigurationOptions Clone()
                 responseTimeout = responseTimeout,
                 DefaultDatabase = DefaultDatabase,
                 ReconnectRetryPolicy = reconnectRetryPolicy,
-                preserveAsyncOrder = preserveAsyncOrder,
                 SslProtocols = SslProtocols,
             };
             foreach (var item in EndPoints)
@@ -458,7 +457,6 @@ public string ToString(bool includePassword)
             Append(sb, OptionKeys.ConfigCheckSeconds, configCheckSeconds);
             Append(sb, OptionKeys.ResponseTimeout, responseTimeout);
             Append(sb, OptionKeys.DefaultDatabase, DefaultDatabase);
-            Append(sb, OptionKeys.PreserveAsyncOrder, preserveAsyncOrder);
             commandMap?.AppendDeltas(sb);
             return sb.ToString();
         }
@@ -537,7 +535,7 @@ private void Clear()
         {
             ClientName = ServiceName = Password = tieBreaker = sslHost = configChannel = null;
             keepAlive = syncTimeout = connectTimeout = writeBuffer = connectRetry = configCheckSeconds = DefaultDatabase = null;
-            allowAdmin = abortOnConnectFail = highPrioritySocketThreads = resolveDns = ssl = preserveAsyncOrder = null;
+            allowAdmin = abortOnConnectFail = highPrioritySocketThreads = resolveDns = ssl = null;
             defaultVersion = null;
             EndPoints.Clear();
             commandMap = null;
@@ -651,9 +649,6 @@ private void DoParse(string configuration, bool ignoreUnknown)
                             DefaultDatabase = OptionKeys.ParseInt32(key, value);
                             break;
                         case OptionKeys.PreserveAsyncOrder:
-#pragma warning disable CS0618
-                            PreserveAsyncOrder = OptionKeys.ParseBoolean(key, value);
-#pragma warning restore CS0618
                             break;
                         case OptionKeys.SslProtocols:
                             SslProtocols = OptionKeys.ParseSslProtocols(key, value);