tests/func: add a test for massive clone

Master can't pass it and following patch fixes it.

Reviewed-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep: clear child vdi for deletion

This will fix a bug that after deletion of clones, we fail to create clones
with the snapshot that we previousy cloned.

Reviewed-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
lib/option: support 'B' notation for byte

Reviewed-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
lib/work: kill a possible memory leaker

Though in reality, this wouldn't happen.

Reviewed-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>