Make the default-switch test tolerate a configured managed SNI switch

TestDefaultAppContextSwitchValues asserted that UseManagedNetworking is false on
Windows, which fails in the managed SNI test leg now that the switch is enabled
process-wide through runtimeconfig.json. Compare the property against AppContext
instead, so the assertion still verifies that the switch is honoured and remains
unchanged when the switch is not configured.

Author: paulmedynski

eng/pipelines/ci/kerberos/linux-setup-step.yml

@@ -107,4 +107,4 @@ steps:
       Invoke-Sqlcmd -Query "SELECT @@VERSION, @@SERVERNAME" -ConnectionString $env:REMOTE_TCP_CONN_STRING
     displayName: Verify SQL connectivity
     env:
-      REMOTE_TCP_CONN_STRING: $(REMOTE_TCP_CONN_STRING)
+      REMOTE_TCP_CONN_STRING: $(REMOTE_TCP_CONN_STRING)

src/Microsoft.Data.SqlClient/tests/UnitTests/Microsoft/Data/SqlClient/LocalAppContextSwitchesTest.cs

@@ -73,7 +73,12 @@ public void TestDefaultAppContextSwitchValues()
         Assert.False(switchesHelper.GlobalizationInvariantMode);
         if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
         {
-            Assert.False(switchesHelper.UseManagedNetworking);
+            // The managed SNI test leg enables this switch process-wide via runtimeconfig.json,
+            // so compare against AppContext rather than assuming the switch is unset.
+            System.AppContext.TryGetSwitch(
+                "Switch.Microsoft.Data.SqlClient.UseManagedNetworkingOnWindows",
+                out bool useManagedNetworking);
+            Assert.Equal<bool?>(useManagedNetworking, switchesHelper.UseManagedNetworking);
         }
         else
         {