Openstack FFU command 'openstack overcloud external-upgrade run --tags system_upgrade_transfer_data' fails with the task 'synchronize both directories'

Issue

During the FFU 13 to 16 you run this command:

openstack overcloud external-upgrade run --tags system_upgrade_transfer_data

But it fails with something like this:

2023-06-15 12:57:20,964 p=19997 u=mistral n=ansible | 2023-06-15 12:57:20.964039 | aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa |      FATAL | synchronize both directories | undercloud -> $source_IP | error={"changed": true, "cmd": "/usr/bin/rsync -v --delay-updates -F --ignore-times --compress --archive --delete   --rsync-path='sudo rsync' --rsh='ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -i ~/transfer_key' /var/lib/openvswitch/ovn/ tripleo-admin@$destination_IP:/var/lib/openvswitch/ovn", "delta": "0:00:00.537386", "end": "2023-06-15 12:57:20.940348", "msg": "non-zero return code", "rc": 23, "start": "2023-06-15 12:57:20.402962", "stderr": "Warning: Permanently added '$destination_IP' (ECDSA) to the list of known hosts.\r\n\nrsync: change_dir \"/var/lib/openvswitch/ovn\" failed: No such file or directory (2)\nrsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1179) [sender=3.1.2]", "stderr_lines": ["Warning: Permanently added '$destination_IP' (ECDSA) to the list of known hosts.", "", "rsync: change_dir \"/var/lib/openvswitch/ovn\" failed: No such file or directory (2)", "rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1179) [sender=3.1.2]"], "stdout": "building file list ... done\n\nsent 62 bytes  received 16 bytes  156.00 bytes/sec\ntotal size is 0  speedup is 0.00", "stdout_lines": ["building file list ... done", "", "sent 62 bytes  received 16 bytes  156.00 bytes/sec", "total size is 0  speedup is 0.00"]}