The LVM add-on reaches GA in v1.9.1 and only supports dm-thin.
Gate the striped option behind a v1.9.1 feature flag, default new
LVM storage classes to dm-thin, and reset a cloned striped type so
older clusters keep the current behaviour.
Related issue: harvester/harvester#11731
Signed-off-by: Vicente Cheng <vicente.cheng@suse.com>