[iOS] Ignore intermittent failing test on XTC (#666)

Xamarin.Forms.Core.iOS.UITests/Tests/Legacy-CellsUITests.cs

@@ -96,6 +96,7 @@ namespace Xamarin.Forms.Core.UITests
 		}
 
 		[Test]
+		[Ignore("Ignore because is only failing on iOS10 at XTC")]
 		[Description("ListView with ImageCells, file access problems")]
 		[UiTest(typeof(ListView))]
 		[UiTest(typeof(ImageCell))]