Follow-up to r44216/r44217 "Followup to r44204. Hardcoding image because it should...

Follow-up to r44216/r44217 "Followup to r44204. Hardcoding image because it should (in theory) work always and forever. If you have a wiki acting as repo and you've overridden the canonical name Image: it's your own fault."
It was noted that the existing code could fail for unusual article path settings including a suffix if only the 'articleUrl' was available. Pretty corner case, and probably breaks a lot of other things, but who knows. :)
Went ahead and refactored this a bit to handle the case and feel a little cleaner to me...
Dropped the private getDescBaseUrl() method since this seems a little easier to handle directly in getDescriptionUrl() now.