Fixes #37043 - Inheritance overrides host facets

This of course has the same problem as the rest of Foreman where it
becomes impossible to specify `nil` as the wanted value, since any
unspecified values are automatically inherited.
But it's still better than being entirely unable to set host-specific
values for facets that inherit.

app/models/concerns/facets/base.rb

@@ -42,7 +42,7 @@ def inherited_attributes(hostgroup, facet_attributes)
         _, facet_config = Facets.find_facet_by_class(self, :host)
 
         if facet_config.has_hostgroup_configuration? && hostgroup
-          facet_attributes = hostgroup.inherited_facet_attributes(facet_config)
+          facet_attributes = hostgroup.inherited_facet_attributes(facet_config).merge(facet_attributes || {}) { |_, left, right| right || left }
         end
         facet_attributes
       end