Ceph storage cluster bootstrap fails with stderr IndexError: list index out of range

Issue

• Bootstrap of a Ceph cluster fails, displaying the following traceback.

  [root@rhel8 ~]# cephadm --verbose --image registry.example.com:5000/rhceph/rhceph-5-rhel8:5-49 bootstrap --mon-ip 198.51.100.65 --cluster-network 198.51.100.0/24 --ssh-user myuser --ssh-private-key /home/myuser/.ssh/id_rsa --ssh-public-key /home/myuser/.ssh/id_rsa.pub --ssh-config /etc/ssh/ssh_config_ceph  --allow-overwrite
  [..]
  /usr/bin/ceph: stderr IndexError: list index out of range
  /usr/bin/ceph: stderr
  Traceback (most recent call last):
    File "/sbin/cephadm", line 9183, in <module>
      main()
    File "/sbin/cephadm", line 9171, in main
      r = ctx.func(ctx)
    File "/sbin/cephadm", line 1970, in _default_image
      return func(ctx)
    File "/sbin/cephadm", line 4828, in command_bootstrap
      prepare_ssh(ctx, cli, wait_for_mgr_restart)
    File "/sbin/cephadm", line 4324, in prepare_ssh
      cli(['cephadm', 'set-user', ctx.ssh_user])
    File "/sbin/cephadm", line 4768, in cli
      ).run(timeout=timeout)
    File "/sbin/cephadm", line 3749, in run
      desc=self.entrypoint, timeout=timeout)
    File "/sbin/cephadm", line 1638, in call_throws
      raise RuntimeError('Failed command: %s' % ' '.join(command))
  RuntimeError: Failed command: /usr/bin/podman run --rm --ipc=host --stop-signal=SIGTERM --net=host --entrypoint /usr/bin/ceph --init -e CONTAINER_IMAGE=registry.example.com:5000/rhceph/rhceph-5-rhel8:5-49 -e NODE_NAME=rhel8 -e CEPH_USE_RANDOM_NONCE=1 -v /var/log/ceph/461e6ffc-530b-4a49-8fed-c4c99e2eb226:/var/log/ceph:z -v /tmp/ceph-tmptyqp7eb7:/etc/ceph/ceph.client.admin.keyring:z -v /tmp/ceph-tmpnz29yuzq:/etc/ceph/ceph.conf:z registry.example.com:5000/rhceph/rhceph-5-rhel8:5-49 cephadm set-user myuser