If the Vault server returns an error, we must report it in the init
container. With this we can properly debug a failing init container.
Resulting container log:
```
oc logs rook-ceph-osd-0-dc6d4d4d-445dg -c encryption-kms-get-kek ⏎
['error performing token check: Vault is sealed']%
```
Signed-off-by: Sébastien Han <seb@redhat.com>