[Nova] Injection metadata disappears after instance resize

--- Environment ---
MOS 9 (ISO build 528)

--- Steps to reproduce ---
1. Launch a VM with injected file:
vim /root/inject.txt
nova boot --flavor m1.micro --image TestVM --nic net-id=832acbbf-9fe0-47e6-97e5-ece8ab7a9f96 --file /root/inject.txt=/root/inject.txt test_vm1

2. Check the content of config drive on the compute node
mkdir /mnt/config/
mount /var/lib/nova/instances/cb4913ab-a884-4d20-9907-aac52c082509/disk.config /mnt/config/

cat /mnt/config/openstack/latest/meta_data.json | jq .files
[
  {
    "content_path": "/content/0000",
    "path": "/root/inject.txt"
  }
]

3. Resize the instance
nova resize test_vm1 m1.tiny
nova resize-confirm test_vm1

4. Check the content of config drive on the new compute node
mkdir /mnt/config/
mount /var/lib/nova/instances/cb4913ab-a884-4d20-9907-aac52c082509/disk.config /mnt/config/
cat /mnt/config/openstack/latest/meta_data.json | jq .files

--- Actual result ---
The information about the injected file is not present in metadata:
cat /mnt/config/openstack/latest/meta_data.json | jq .files
null

--- Expected result ---
The information about the injected file is present in metadata:
cat /mnt/config/openstack/latest/meta_data.json | jq .files
[
  {
    "content_path": "/content/0000",
    "path": "/root/inject.txt"
  }
]