storage/reflink: reorder start() to be more readable
storage/reflink: reorder start() to be more readable

This also makes slightly more sense in the exotic (and currently unused)
case of restarting a crashed snap_on_start *and* save_on_stop volume.

marmarek/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin