sheep, dog: add "block_size_shift" option to cluster format command

This patch changes for specifying cluster default block_size_shift.

Signed-off-by: Teruaki Ishizaki <ishizaki.teruaki@lab.ntt.co.jp>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
sheep, dog: add selectable object_size support of VDI operation

Data object size was fix to 4MB and not selectable.
This patch add feature to select data object size of VDI.

If you want to use 8MB(2^23) data object_size, specify the
block_size_shift bit num to 23.

ex) dog vdi create -z 23 testvdi 100M

Signed-off-by: Teruaki Ishizaki <ishizaki.teruaki@lab.ntt.co.jp>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
dog: revert the change for output of "dog vdi list" manually

This patch is a temporal thing. The previous commit (ae3c78b9651cc2)
introduced change of "dog vdi list" command, it added a new field of
block size shift.

It breaks existing tests/fucntional. So this patch remove the
change. After the tests updated correctly, this patch can be reverted
simply.

Cc: Teruaki Ishizaki <ishizaki.teruaki@lab.ntt.co.jp>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>