Canonical URL is not consistent when parked domains are in use. 

## Bug Description
A site using parked subdomains over the main domain may end up with conflicting canonical values for the same content. 
ie. canonical URLs containing the parked domain rather than the main site domain. 

## Expected Behavior
The site's main domain to be used in generated canonical URLs, even if the  content is loaded via a parked domain URL. 

