nix the string interpolation

thanks Keenan and Jason :)

app/models/mixins/aggregation_mixin/methods.rb

@@ -39,11 +39,11 @@ def all_storages
     end
 
     def aggregate_hardware(from, field, targets = nil)
-      from      = from.to_s.singularize
+      from      = from.to_s.singularize.to_sym
       select    = field == :aggregate_cpu_speed ? "cpu_total_cores, cpu_speed" : field
       targets ||= send("all_#{from}_ids")
       targets   = targets.collect(&:id) unless targets.first.kind_of?(Integer)
-      hdws      = Hardware.where("#{from}_id".to_sym => targets).select(select)
+      hdws      = Hardware.where(from => targets).select(select)
 
       hdws.inject(0) { |t, hdw| t + hdw.send(field).to_i }
     end