[Release 1.21] - s3 snapshots do not show in the rancher 2.6 UI

[briandowns]

Backport of #1551

[brandond]

v1.21.3+rke2r2 or v1.21.4+rke2r1?

[davidnuzik]

Testing with Rancher/UI will be covered via rancher/dashboard#3693
I will test just standalone RKE2 here in this issue.

My checks PASSED

Reproduction Steps:

Not required as I fully understand the issue.

Validation Steps:

Host OS: Ubuntu 20.04 amd64
RKE2 version: v1.21 release branch, commit 355cdae7ba6240d1c4f9d68dab08c344a8490dbb (effectively v1.21.3-rc5+)
Tested with a 1-node rke2 cluster.

Validation steps:

1. Create /etc/rancher/rke2/config.yaml with the following content. Take note we specify an s3 folder (which is what we are focusing our testing on here as per the code change).

"write-kubeconfig-mode": "0644"
"etcd-s3": true
"etcd-s3-access-key": "REDACTED_ACCESS_KEY"
"etcd-s3-bucket": "dave-test99"
"etcd-s3-endpoint": "s3.us-east-2.amazonaws.com"
"etcd-s3-folder": "test121"
"etcd-s3-region": "us-east-2"
"etcd-s3-secret-key": "REDACTED_SECRET_KEY"
"etcd-s3-skip-ssl-verify": true
"etcd-snapshot-retention": 2
"etcd-snapshot-schedule-cron": "03 * * * *"

2. Install RKE2 via the install.sh script:
   curl -sfL https://get.rke2.io | INSTALL_RKE2_COMMIT=18bc38d83852154d0a6f7cbc96f9c21aa5603d56 sh -
3. Ensure the config.yaml took properly by checking the rke2.io/node-args annotation on the node with kubectl.
4. A snapshot is automatically taken as per my cron schedule.
5. An on-demand snapshot is successful:
   rke2 etcd-snapshot --s3 --s3-skip-ssl-verify --s3-region "us-east-2" --s3-bucket "dave-test99" --s3-folder "test121" --s3-access-key "REDACTED_ACCESS_KEY" --s3-secret-key "REDACTED_SECRET_KEY"

Result:
My scheduled snapshots and my on-demand snapshot are successfully uploaded to the bucket in the correct folder