Avoid races with HA on "python manage.py syncdb"

We didn't have any synchronization for it because this is run in a
notification. But it's actually easy to force a synchronization there
too, by putting the template creating the notification as part of the sync.
Configure horizon before configuring the vhost for horizon in apache

This sounds much safer, and I believe it actually prevents a bug where,
sometimes, static files are not being generated by horizon when using HA
(likely because haproxy is opening a connection to apache and the
not-yet-configured horizon, which could be what is breaking things).
Fix apache with HA not running until second chef-client run

It doesn't work on first run because we don't have yet the proper
attributes set when creating the pacemaker resource.
Merge pull request #182 from vuntz/syncdb-ha

Avoid races with HA on "python manage.py syncdb" + Move configuration of vhost later
Use helpers from new crowbar-openstack cookbook