Allow to source extra settings from reclass model
Allow to source extra settings from reclass model

Some models may require additional settings like EXTRA_FORMULAS to be specified
for initial setup like AiO model. This patch will allow to keep such extra
settings with cluster model in reclass
 <reclass_path>/classes/cluster/<cluster_name>/extra_settings

Change-Id: Ib861f1f81d82444f98ce37a9315342e3c8df22b2

salt-formulas/salt-formulas,salt-formulas/salt-formulas,salt-formulas/salt-formulas