Do not reset datasize after a fake snapshot
If we reset dataSize from SnapshotManager's fake snapshot, we would
not have correctly accounted for on-disk size.
Fix this by exposing a simple knob, which allows suppressing dataSize
update during snapshotCommit().
JIRA: CONTROLLER-1957
Change-Id: I553ddb523ac8504892cc5353bfe4b002c25436ce
Signed-off-by: tadei.bilan <tadei.bilan@pantheon.tech>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit
ff29db5dc6012f77bbe53f57ddce929b0de093b3)