Update db password migration script to remove node attributes

On update, we want to use the db password from the proposal / role, and
not the one that might have been generated on the node (through the
cookbook). As the password is a "normal" attribute on the node, but a
"default" attribute on the role, the old one from the node is used.
Which means we really need to remove it to get the new one used.

To minimize config changes, we actually import the password from one
node (which should be good enough in most cases as we allow only one
heat proposal, so only one node should have the password).
Manage heat services via pacemaker clone LWRP

create clone resource for group, not for individual resources
Merge pull request #52 from vuntz/drop-db-node

Update db password migration script to remove node attributes
Merge pull request #53 from vuntz/sync-marks

Use new synchronization helpers to avoid races when deploying with HA
Merge pull request #48 from jsuchome/clones

Manage heat services via pacemaker clone LWRP
Add synchronization marks around the creation of pacemaker resources