block: return status from bdrv_append and friends

block: return status from bdrv_append and friends

The recommended use of qemu error api assumes returning status together
with setting errp and avoid void functions with errp parameter. Let's
improve bdrv_append and some friends to reduce error-propagation
overhead in further patches.

Choose int return status, because bdrv_replace_node_common() has call
to bdrv_check_update_perm(), which reports int status, which seems
correct to propagate.

Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
Message-Id: <20210202124956[email protected]>
Reviewed-by: Alberto Garcia <[email protected]>
Signed-off-by: Eric Blake <[email protected]>