Ceph

When an rbd image is mirrored and migrated between pools (rbd migration) the mirroring mode changes from "snapshot" (per migration) to "journal" (post migration).

Expected behavior: Mirroring mode does not change (stays mode snapshot)

To reproduce:
- setup up image based mirroring on two separate pools
- enable image mirroring type snapshot (rbd mirror miage enable pool/imagename)
- confirm the "mirroring mode: snapshot)
- Use rbd migration to migration image between pools
- After the image has succesfully migrated check the "mirroring mode: journal"

This was tested on 18.2.2 (cephadm)