Provide a more flexible variables affectation

[wilfriedroset]

Currently Milkcheck provide variables that would be used for every target. In an heterogeneous cluster, target may not have the same value for the same variable name (e.i: firmware version). It would be nice if Milkcheck provide a declarative system that respond to this need.

VARIABLES:
    bios: default_value
    bios.node[1-10]: testing_value
    bios.@different_hardware: specific_value

By default, all target will use default_value, node[1-10] will use testing_value, and target in the nodeset @different_hardware will use specific_value.

If node1 is in @different_hardware we should use the more precise value which would be use of the target name:

1. target name (bios.foo1)
2. nodeset (bios.foo[1-10])
3. clustershell group (bios.@compute)
4. no suffix (bios)

[degremont]

This sounds very like CHAOS genders. Maybe, we should consider adding this feature directly inside ClusterShell.