Add proper requires

[Cedric Bosdonnat]

When adding custom states to configure the cluster after its creation, the user needs to add requires in his states. However these may break the linear order of the formula.

In order to make the formula more robust a few more requires would be needed. For instance in cluster/create.sls something like this would be needed on the bootstrap-the-cluster state:

     {% if cluster.watchdog is defined %}
     {% if cluster.watchdog.device is defined %}
     - require:
       - kmod: {{ cluster.watchdog.module }}
     {% endif %}
     {% endif %}

This example is one I encountered, but is surely not the only one.