Verified with OCP build 4.3.0-0.nightly-2020-04-23-225015,
$ master=$(oc get nodes | grep master | head -1 | cut -d " " -f1)
$ oc debug node/$master
sh-4.2# chroot /host
sh-4.4# cd /var/log/pods
sh-4.4# grep -nr 'unable to load initial CA bundle for' *kube-apiserver*
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, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.