Disable Async cancellation tests on Kerberos/Managed Instance pipelines (dotnet#4311)

Author: cheenamalhotra

src/Microsoft.Data.SqlClient/tests/ManualTests/DataCommon/DataTestUtility.cs

@@ -387,6 +387,8 @@ private static Task<string> AcquireTokenAsync(string authorityURL, string userID
 
         public static bool IsKerberosTest => !string.IsNullOrEmpty(KerberosDomainUser) && !string.IsNullOrEmpty(KerberosDomainPassword);
 
+        public static bool IsNotKerberosTest => !IsKerberosTest;
+
         #nullable enable
 
         /// <summary>

src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/AsyncTest/AsyncCancelledConnectionsTest.cs

@@ -25,7 +25,10 @@ public class AsyncCancelledConnectionsTest
         private Random _random;
 
         // Disabled on Azure since this test fails on concurrent runs on same database.
-        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsNotAzureServer))]
+        // Disabled on Kerberos and Managed Instance pipelines due to environment-specific instability.
+        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup),
+            nameof(DataTestUtility.IsNotAzureServer), nameof(DataTestUtility.IsNotManagedInstance),
+            nameof(DataTestUtility.IsNotKerberosTest))]
         [InlineData(true)]
         [InlineData(false)]
         public async Task CancelAsyncConnections(bool useMars)