iotests: Enhance 223 to cover multiple bitmap granularities

Testing granularity at the same size as the cluster isn't quite
as fun as what happens when it is larger or smaller.  This
enhancement also shows that qemu's nbd server can serve the
same disk over multiple exports simultaneously.

Signed-off-by: Eric Blake <eblake@redhat.com>
Tested-by: John Snow <jsnow@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2 files changed