Fix constraints refering to cloned resources

* Warn when user tries to create a constraint for a clone
  or master/slave child.
* Move the constraints from a group to the clone or master when cloning
  the group. Previously worked only for the plain resources.
Require --force when using --rrpmode active
Fixed variable mis-spelling when fixing for Ruby 1.8.7
Fixed error when viewing cluster and cluster is not started
Fix error in rhel6 detection
Fixed getting node attributes.

Function get_node_attributes returns all attributes, not just one.
Added support for node attributes