Set the root propagation based on the properties of volumes and default
mounts. To remain compatibility, follow the semantics of Docker. If a
volume is shared, keep the root propagation shared which works for slave
and private volumes too. For slave volumes, it can either be shared or
rshared. Do not change the root propagation for private volumes and
stick with the default.
Fixes: #1834
Signed-off-by: Valentin Rothberg <vrothberg@suse.com>
