[BUGFIX] Redirect on direct access to overlayed mountpoint

When the user directly accesses a page that is a mountpoint that
should be overlayed with the contents of the mounted page he will
be redirected to the target page within the mounpoint context.

Releases: 6.2
Resolves: #59382
Change-Id: Ie00c8210b39d2934b410d782799e4fc90efa8c5c