ScrollView doesn't remove a view that was previously added on both versions.

[BDisp]

This unit test will fail:

		[Fact, AutoInitShutdown]
		public void Remove_Added_View_Is_Allowed ()
		{
			var sv = new ScrollView () {
				Width = 20,
				Height = 20,
				ContentSize = new Size (100, 100)
			};
			sv.Add (new View () { Width = Dim.Fill (), Height = Dim.Fill (50), Id = "View1" },
				new View () { Y = 51, Width = Dim.Fill (), Height = Dim.Fill (), Id = "View2" });

			Application.Top.Add (sv);
			Application.Begin (Application.Top);

			Assert.Equal (3, sv.Subviews.Count);
			Assert.Equal (2, sv.Subviews [0].Subviews.Count);

			sv.Remove (sv.Subviews [0].Subviews [1]);
			Assert.Equal (3, sv.Subviews.Count);
			Assert.Single (sv.Subviews [0].Subviews);
			Assert.Equal ("View1", sv.Subviews [0].Subviews [0].Id);
		}