Simple address outside site should work with all hosts

Description

Scenario

• Multi-site (3 sites) Episerver setup running in the same IIS app pool
• Single language across all sites
• All sites have separate domains, and one site is configured with a wildcard host entry (as is necessary for Episerver Find to index the shared content).
• Content structure has a shared folder of content that can be used on any of the three sites.

We built our own partial router / access control to decide if a piece of shared content is available in each site.
When using Simple addresses, those for shared content are only resolved for the website configured with the wildcard binding.

For example:
www.site1.com/simple - resolves as expected to the content with the short url 'simple', which lives outside of any configured path.
www.site2.com/simple - returns a 404

I can switch this behavior around by changing which site has the wildcard host mapping. Whichever site has the wildcard mapping resolves the simple urls.

Expected

Honor the simple address for any site for any content that lives outside of a configured start page. For example, www.site1.com/simple and ww.site2.com/simple both resolve to the same content, regardless of how the wildcard entry is mapped.

see http://world.episerver.com/forum/developer-forum/-Episerver-75-CMS/Thread-Container/2017/5/multi-site-and-simple-address-behaviour-for-pages-outside-of-a-site-start-page/