corosync: Add attribute to not start corosync on boot after fencing

If the node[:corosync][:require_clean_for_autostart] attribute is set to
true, then corosync will not start on boot automatically, nor through
chef-client, if the file /var/spool/corosync/block_automatic_start
exists.

On proper shutdown, one new init script (corosync-shutdown) is used to
remove that file and stopping corosync, resulting in the next boot to
have corosync starting.

This allows to not start corosync after fencing, to avoid a never-ending
deathmatch, or a fencing loop.
Expose require_clean_for_autostart attribute in crowbar
Add "automatic" option in crowbar for require_clean_for_autostart

By default, we want to use require_clean_for_autostart for a two-nodes
cluster, and only in that case. This is something that we do at the
orchestration layer with crowbar, by wrapping this value in a tri-state
attribute.
Fix potential use of undefined variable
Merge pull request #88 from vuntz/no-auto-start-on-fencing

corosync: Add attribute to not start corosync on boot after fencing
Make sbd work with partitions too, not just whole disks

The disk claiming bit was restricting usage of devices so that it only
worked for whole disks. Now, if we get a partition, then we first
identify the disk the partition is on and then try to claim that disk.

https://bugzilla.novell.com/show_bug.cgi?id=875843
Merge pull request #98 from vuntz/sbd-partitions

Make sbd work with partitions too, not just whole disks
Install xfsprogs if we're using xfs for a DRBD device
sbd: Wait for cluster to be up after corosync restart

Every time we start corosync, we need to wait for the cluster to be up.
And when we use sbd, we restart corosync to start sbd, so we need to
wait there too.
Merge pull request #101 from vuntz/install-xfs

Install xfsprogs if we're using xfs for a DRBD device
Fix installation of xfsprogs
Merge pull request #102 from vuntz/sbd-sync

sbd: Wait for cluster to be up after corosync restart
Merge pull request #103 from vuntz/install-xfs-fix

Fix installation of xfsprogs
fix interpolation of pid
Merge pull request #104 from aspiers/pid-interpolation-fix

fix interpolation of pid