Fixed in coreos-installer-0.9.0-5.rhaos4.8.el8, which is built and in plashet. Awaiting bootimage bump.
Verified based on https://bugzilla.redhat.com/show_bug.cgi?id=1960485#c29 OCP image registry.ci.openshift.org/ocp-s390x/release-s390x:4.8.0-0.nightly-s390x-2021-08-18-161834 is running with RHCOS 48.84.202108181304-0 and has a boot image of 48.84.202106302220-0, which has coreos-installer 0.9.0-6.rhaos4.8.el8 that contains the fix.
OpenShift engineering has decided to NOT ship 4.8.6 on 8/23 due to the following issue. https://bugzilla.redhat.com/show_bug.cgi?id=1995785 All the fixes part will be now included in 4.8.7 on 8/30.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (OpenShift Container Platform 4.8.9 bug fix), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2021:3247