Fix GitHub CI from forks
The previous version only worked if the PRs were created in the same project and not from forks. Fix this.
Note that the kpet-db CI is not fixed as the situation with that one is more complicated and may need adjustments in that repo as well, however the situation is not as critical with that one as the development tends to happen in the project directly.
Signed-off-by: Veronika Kabatova vkabatov@redhat.com