Add unit test for HasDriveAutoMounting()

Cannot unit test SessionStateInternal.Drives() (where this feature query
is used) without a testable mock of PowerShell.

src/ps_test/ps_test.cs

@@ -13,6 +13,7 @@ namespace PSTests
             PlatformTests.TestHasCom();
             PlatformTests.TestHasAmsi();
             PlatformTests.TestUsesCodeSignedAssemblies();
+            PlatformTests.TestHasDriveAutoMounting();
 
             PSTypeExtensionsTests.TestIsComObject();
 

src/ps_test/test_CorePsPlatform.cs

@@ -25,5 +25,10 @@ namespace PSTests
         {
             Assert.False(Platform.UsesCodeSignedAssemblies());
         }
+
+        public static void TestHasDriveAutoMounting()
+        {
+            Assert.False(Platform.HasDriveAutoMounting());
+        }
     }
 }