Currently, while preparing a volume for snapshot,
the depthToAvoidFlatten is set to 2. This accounts one
for snapshot and another since parent of the volume is
flattened.
This commit modifies the depth to 3 to also account for
future PVC restore since
- snapshot alone is useless and it is very likely to be restore
at one point in time.
- this ensures snapshot is not flattened when restore does occur.
- flattening of snapshot in the above case will make the snapshot
no longer eligible for changed block tracking(snap diff)
operation.
- maintain similarity with PVC-PVC clone operation which currently
depthToAvoidFlatten set to 1.
Signed-off-by: Rakshith R <rar@redhat.com>