bump sheepdog 0.6 + add new features v2

bump sheepdog 0.6 + add new features v2

This bump sheepdog to 0.6, with some changes:

Now, we only 1 daemon to manage multiple disks.

default root directory is :

/var/lib/sheepdog/

This is the default if you don't have dedicated disk.
Both metadatastore and objet store are in the root directory.

If you want to use, 1 or more dedicated disk:

simply create mounts in

/var/lib/sheepdog/disc0
/var/lib/sheepdog/disc1
/var/lib/sheepdog/discN

No more limit in number of disk, and no more need of a startup file tricks.

The metadata-store is always in /var/lib/sheepdog/.  (spof, so you need raid)
But the object-storage are in /var/lib/sheepdog/discN. You can hotplug/unplug theses disks, have failures,...

https://github.com/collie/sheepdog/wiki/Multi-disk-on-Single-Node-Support

You can also use a journal on separate disk, like ssd, for fast write.
simply create a mount:

/var/lib/sheepdog/journal

Some tunnables variables in /etc/default/sheepdog:

ROOTDIR=/var/lib/sheepdog/
By example,users can change it to /var/lib/vz/sheepdog  if they want (As this is the location where we have the more space by default)

JOURNALSIZE=256
User can tune the journal size, 256M by default

Signed-off-by: Alexandre Derumier <aderumier@odiso.com>