[sheepdog] [ANNOUNCE, CAUTION] sheepdog stable release v0.8.1_rc1

[Hitoshi Mitake]

Hi sheepdog users and developers,

I released v0.8.1_rc1 of stable branch. You can download a source
archive from these URLs:
tar.gz: https://github.com/sheepdog/sheepdog/archive/v0.8.1_rc1.tar.gz
zip: https://github.com/sheepdog/sheepdog/archive/v0.8.1_rc1.zip

This update contains a bunch of important improvements related to
zookeeper cluster driver, snapshot, and a case of massive objects.

I have to emphasis on the point that updating from v0.8.0 to
v0.8.1_rc1 requires "-u" option, because it contains updating store
format. Sorry for inconvenience but the format update is a necessary
change for clusters which store many objects.

If no one disagrees about this release candidate in 2 days, it will be
v0.8.1 officially.

Below is a summary of commits backported after the release of v0.8.1_rc0:

Hitoshi Mitake (2):
      sheep: reload config after successful migration
      sheep: migrate format from v3 to v4

Liu Yuan (7):
      tests/func: add a test for massive clone
      sheep: clear child vdi for deletion
      sheep/vdi: fix vdi snapshot deletion
      util: remove unused functions
      dog/farm: register vdi for 'snapshot load operation'
      sheep: kill is_erasure_obj()
      sheep: store ec_index in the pathname instead of in xattr

Robin Dong (6):
      sheep: avoid dead loop when zookeeper session is expired
      sheep/cluster: let local_lock() support nested
      sheep/cluster: delete znodes when leaving cluster
      sheep/cluster: use wrapper function to create ephemeral znode
      sheep/cluster: change output format in sheep log
      sheep/md: change process of for_each_object_in_wd() to multi-threads

Thanks,
Hitoshi