qemu-iotests/067: Avoid blockdev-add with id

We want to remove the 'id' option for blockdev-add. This removes one
user of the option and makes it use only node names.

In order to keep the test meaningful, some instances of query-block that
want to check whether the node still exists and would now turn up empty
must be converted to query-named-block-nodes (which also return the
protocol level node, but that shouldn't hurt).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
