Routing URL fix

What does this MR do?

I noticed that due to changes made in !1602 (merged), the URIs returned by RouteHelper::getSelf can be incorrect for xhr.php and xhrapp.php URLs. This MR fixes that.

Note that this is only necessary until the web server configuration gets adjusted to play properly with Symfony.

How confident are you it won't break things if deployed?

confident

Links to related issues

• !1602 (merged)

• dragonfruit-ansible#4

Screenshots (if applicable)

The issue and how it's fixed:

See the value of $originalRequestUri for what it is currently.

See the value of $fixedRequestUri for what it looks like after being fixed.

Checklist

• very small scope of this fix, so no test needed really
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• use "state:" labels to track this MR's state until it was beta tested
• added an entry to CHANGELOG.md