Missing horizontal scroll in grid-sample-toolbar-pinning sample when multiple columns are pinned

[dobromirts]

1. Open https://www.infragistics.com/products/ignite-ui-angular/angular/components/grid/column-pinning#angular-grid-column-pinning--example
2. Pin all columns
3. Observe that the horizontal scroll is not visible anymore
4. Unpin 2 columns - the scroll is still not visible - the user is not able to interact with these columns