Describe the bug
Kubernetes >= v1.17 no longer supports csi version v0.3
We updated the components and the min kubernetes version but did not change the default advertised csi version

The relevant code needs to be changed here: https://github.com/longhorn/longhorn-manager/blob/0cf54c5c79dbc5b91a3bb31bad25fbd0ecd61b94/app/csi.go#L36

Environment:

• Longhorn version: v1.1.3 and v1.2.x

Additional context
We should be safe to advertise at least https://github.com/container-storage-interface/spec/releases/tag/v1.2.0
There is some newer abilities in the newer versions that we are not yet taking advantage off.
We might want to implement ListVolumes which is used for attachment verification after the volume-controller refactor for v1.3