WIP: DNM: Add support for an array of equalogic backends

Modifies the AttributeParamStorage to support an array of items
Oh -- actually, an even easier test case would be to just pick 'HA' initally and see if this validation is triggered if you don't pick a back end -- the default value is lvm true, so I suspect this will let the user go on and not choose a non-LVM back end (and won't force the 'lvm == true' to be false at the param level.