rpcserver+subrpcserver: don't use global cfg

subrpcserver_config.go

@@ -80,7 +80,7 @@ type subRPCServerConfigs struct {
 //
 // NOTE: This MUST be called before any callers are permitted to execute the
 // FetchConfig method.
-func (s *subRPCServerConfigs) PopulateDependencies(cc *chainControl,
+func (s *subRPCServerConfigs) PopulateDependencies(cfg *Config, cc *chainControl,
 	networkDir string, macService *macaroons.Service,
 	atpl *autopilot.Manager,
 	invoiceRegistry *invoices.InvoiceRegistry,