Use Fedora 29 artifacts instead of Fedora 28, since 28 is now end-of-life. Also rename `ci/fah28-insttests.sh` -> `ci/fah29-insttests.sh` and use the https://getfedora.org/atomic_qcow2_latest redirect URL for the latest Fedora Atomic Host 29 image. Closes: #1871 Approved by: jlebon