Conceptually, snapshots have to be taken while the pod and thus the volume
exist. Snapshotting has an issue where flushing of data is not guaranteed while
the volume is still staged on the node, so the test relied on deleting the pod
and checking for the volume to be unused. That part of the test cannot be done
for ephmeral volumes.
This adds a new test pattern and uses it for the inline volume tests. Because
the kind of volume now varies more, validation of the mount or block device is
always done by the caller of TestEphemeral.
CSI driver need to pass special mount opts to XFS filesystem to be able to
mount a volume + its clone or its restored snapshot on the same node. Add a
test to exhibit this behavior.
The test is optional for now, giving CSI drivers time to fix it.