By introducing a SyncInfo interface, the `getLastSyncInfo` function can
be removed from the csi-addons/rbd package. Getting details from an RBD
mirror status, should be part of the main internal/rbd package, the
CSI-Addons components should only use the internal API, and not add any
parsing logic.
This makes it easier to enhance the SyncInfo interface in the future.
Signed-off-by: Niels de Vos <ndevos@ibm.com>
