ci_fairy: Include commit SHA in junit error

It is already included in the testsuite name, but that isn't shown
in gitlab's UI, with the result that the front-page error report
is often useless and the user has to check out the pipeline logs.

Signed-off-by: Florian Müllner <fmuellner@gnome.org>
2 jobs for master in 1 minute and 56 seconds (queued for 1 second)
Child pipeline (parent)
Status Job ID Name Coverage
  Base Image Build
passed #7645399
ci-fairy-base-image

00:00:12

 
  Image Build
passed #7645400
ci-fairy-image

00:01:44