LVHDSR: convert VDI.ref retured by get_snapshot_of to vdi_uuid#781

AnthoineB wants to merge 4 commits intoxapi-project:masterxapi-project/sm:masterfrom

xcp-ng:abo-convert-vdi-ref-to-vdi-uuid-in-get-snapshot-ofxcp-ng/sm:abo-convert-vdi-ref-to-vdi-uuid-in-get-snapshot-ofCopy head branch name to clipboard