Sticky columns show scrolled data between them.

#### What is the expected behavior?
Sticky columns should not show scrolled data between them.

#### What is the current behavior?
When making multiple columns sticky and resize the screen, Scrolled data can display between the sticky columns.

#### What are the steps to reproduce?
Used the stackblitz sticky column example. https://stackblitz.com/edit/angular-ay2dr9?file=app%2Ftable-sticky-columns-example.html

Made the first 3 columns sticky and the fourth column started to display between column 2 and 3.


#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?

#### Is there anything else we should know?

Reproduce the issue using the StackBlitz example at app/table-sticky-columns-example.html, with the first three columns sticky and the viewport resized. Then trace the Angular Material table sticky-column behavior to find why scrolled data appears between sticky columns. Done means the sticky columns remain contiguous without showing intervening scrolled data.

Written by the indexing model from the issue text.