RHEL 8.4: qcow2 images can now be used by older QEMUs

Previously, the guest image for RHEL 8.4 was only usable by QEMU 1.1 and newer. However, this image should be usable on RHEL 6 that ships an older version of QEMU. This is now fixed and the guest image can be now used by QEMU 0.10 and newer.