tests/008: read vdi in paralell

We can read each vdi in parallel for better performance.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
tests: remove directory surely

rm -rf fails if new files are created before rm is completed.  This
patch renames the directory beforehand so that sheep cannot creates
new objects in it any more.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
trivial: misc fixes of comments

This patch fixes some incorrect comments:
1. group.c: colosync -> corosync
2. sockfd_cache.c: vnode -> node
3. sheep_priv.h: past -> part

1 is a very trivial mistake. 2 wouldn't cause a serious confusion but
the description is not correct. vnode is a concept of consisntent
hashing and it is not a something connect to. 3 would be
confusing. Because the way of dealing with exceptional nodes is subtle
and hard to understand.

Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>