openqa: Test s3-image on master
Writing up a discussion from today in #gnome-os.
The s3-image job runs on every 'master' pipeline and pushes an ISO to os.gnome.org.
The iso-installer-x86_64 job does not run on every pipeline and is slow to run when started manually (#396).
OpenQA tests are available by running 'test-iso-installer-x86_64' which depends on iso-installer-x86_64.
In order to have OpenQA testing on all 'master' pipelines, lets change 'test-iso-installer-x86_64' to 'test-s3-image' and run it every time.
This will break the 'pre-merge' testing workflow which nobody was using anyway. Plan to fix that: #601