[5.1.1] Fix | TransactionScope connection issue when Enlist is enable, Pooling is disabled and network connection type is Redirect (#1967)

Author: lcheunglci

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlInternalConnectionTds.cs

@@ -1235,7 +1235,7 @@ private void CompleteLogin(bool enlistOK)
 
             // for non-pooled connections, enlist in a distributed transaction
             // if present - and user specified to enlist
-            if (enlistOK && ConnectionOptions.Enlist)
+            if (enlistOK && ConnectionOptions.Enlist && RoutingInfo == null)
             {
                 _parser._physicalStateObj.SniContext = SniContext.Snix_AutoEnlist;
                 Transaction tx = ADP.GetCurrentTransaction();

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/SqlInternalConnectionTds.cs

@@ -1500,7 +1500,7 @@ private void CompleteLogin(bool enlistOK)
 
             // for non-pooled connections, enlist in a distributed transaction
             // if present - and user specified to enlist
-            if (enlistOK && ConnectionOptions.Enlist)
+            if (enlistOK && ConnectionOptions.Enlist && _routingInfo == null)
             {
                 _parser._physicalStateObj.SniContext = SniContext.Snix_AutoEnlist;
                 SysTx.Transaction tx = ADP.GetCurrentTransaction();

src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/TransactionTest/TransactionTest.cs

@@ -46,8 +46,7 @@ public static class TransactionTest
         public static void ReadNextQueryAfterTxAbortedPoolEnabled(string connString)
             => ReadNextQueryAfterTxAbortedTest(connString);
 
-        // Azure SQL has no DTC support
-        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsNotAzureServer))]
+        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup))]
         [MemberData(nameof(PoolDisabledConnectionStrings))]
         public static void ReadNextQueryAfterTxAbortedPoolDisabled(string connString)
             => ReadNextQueryAfterTxAbortedTest(connString);