Fix class loading for RouteAccessRule metadata models

Add require statements for RouteAccessRuleLabelModel and
RouteAccessRuleAnnotationModel to app/models.rb.

Rails autoloading is disabled for app/** so all models must be
explicitly required. This fixes the error:
  uninitialized constant VCAP::CloudController::RouteAccessRuleLabelModel

Author: rkoster

app/models.rb

@@ -70,6 +70,8 @@
 require 'models/runtime/revision_sidecar_process_type_model'
 require 'models/runtime/route'
 require 'models/runtime/route_access_rule'
+require 'models/runtime/route_access_rule_label_model'
+require 'models/runtime/route_access_rule_annotation_model'
 require 'models/runtime/space_routes'
 require 'models/runtime/space_quota_definition'
 require 'models/runtime/stack'