With the change of the CRI-O jobs to use butane, we now have a
verification for base64 data urls in place. This means that the
following URL is invalid:
```
data:text/plain;base64,GCE_SSH_PUBLIC_KEY_FILE_CONTENT
```
This means we have to pass valid base64 to the URL. To fix that, we now
allow to inject SSH key values with both, the
`GCE_SSH_PUBLIC_KEY_FILE_CONTENT` field and its base64 encoded variant.
Signed-off-by: Sascha Grunert <sgrunert@redhat.com>