fix(openstack): wait for volume attachment state

[Dong Ma (larainema)]

Summary

• wait for migrated volumes to be available and attachment-free before attaching them to the MigrateKit instance or booting the final VM
• detach volumes based on Nova/Cinder attachment state instead of relying on local /dev/disk/by-id discovery
• return disconnect failures from copy cycles so cutover does not continue while volumes are still attached
• add configurable volume create/attach/detach timeouts and recover orphaned reserved volumes with no attachments