Bug: Homepage shifting of components happens when menu flyout is opened.

Problem/Motivation

When opening the offcanvas main menu for the site, there is a shift in some of the page components as container widths and left / right margins are recalculated when the scrollbar becomes invisible as the menu is opened / closed. Scrollbar is visible when menu is closed, but is hidden when the menu is open

Components affected are:
* nav #toolbar-bar: Width recalculates when scrollbar becomes hidden upon opening the application offcanvas menu
* header [role="banner"] > section: Left and right margins (set to auto) recalculate when scrollbar becomes hidden upon opening the application offcanvas menu

Steps to reproduce

* Install Demo Commerce with Belgrade theme
* Navigate to home page
* Toggle the off-canvas menu open and closed, observe the right shift of the above mentioned components

Tested in Chrome, Firefox and Safari