tests/functional: add a new test for vdi check with the condition nr_zones < inode->nr_copies

The newly added test checks that "dog vdi check" can check and recover
lost inode objects well under the condition of nr_zones <
inode->nr_copies. Previous "dog vdi check" rises panic in such a case.

Reviewed-by: Marcin Mirosław <marcin@mejor.pl>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
dog: caliculate a number of zones

New "dog vdi check" requires a number of zones. This patch lets dog
caliculate a number of zones when a subcommand has a flag
CMD_NEED_NODELIST.

Reported-by: Marcin Mirosław <marcin@mejor.pl>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
checkpatch: remove obsolete rule of min_t/max_t

The souce tree of sheepdog doesn't have min_t/max_t.

Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>