[Qemu-block] qemu-io aborts at quit after reopen

[Fam Zheng]

Hi Kevin,

This happens both on master and on your block-next tree:

    $ qemu-io -f raw null-co:// -c 'reopen -r'
    Unexpected error in bdrv_check_perm() at /stor/work/qemu/block.c:1437:
    Block node is read-only
    Aborted

It seems bs->read_only and perms go out of sync when bdrv_reopen() toggles the
former.

Something is missing here?

Fam