Ceph » rbd

The current image-sync state machine should be tweaked to support throttling for both full image sync vs delta image syncs since we won't want hundreds of snapshot-mirrored images to be performing full-image scans across the clusters. The image-sync state machine should also no longer create "sync" snapshots for snapshot mode since it should instead re-use the existing mirror primary snapshots from the remote side.

The replayer will determine if it has finished the initial full sync and request either a full or delta sync slot from the leader rbd-mirror daemon. If idle, it will wait for a snapshot update event from the remote image and schedule itself for a delta sync if a new primary mirror snapshot was created.