migration: Always report an error in block_save_setup()

This will prepare ground for future changes adding an Error** argument
to the save_setup() handler. We need to make sure that on failure,
block_save_setup() always sets a new error.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240320064911.545001-4-clg@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
1 file changed