[openstack|identity] Correction in Roles#all method

User#roles should be calling Service#list_roles_for_user_on_tenant
directly and not use Roles#all since the latter is actually a method
for getting all roles in the Identity Service

lib/fog/openstack/models/identity/roles.rb

@@ -7,13 +7,8 @@ module Fog
       class Roles < Fog::Collection
         model Fog::Identity::OpenStack::Role
 
-        attribute :user
-        attribute :tenant
-
         def all
-          requires :user, :tenant
-          load(connection.
-            list_roles_for_user_on_tenant(tenant.id, user.id).body['roles'])
+          load(connection.list_roles.body['roles'])
         end
 
         def get(id)

lib/fog/openstack/models/identity/user.rb

@@ -54,14 +54,8 @@ module Fog
           true
         end
 
-        def roles
-          return Array.new unless tenant_id
-          tenant = Fog::Identity::OpenStack::Tenant.
-            new(connection.get_tenant(tenant_id).body['tenant'])
-
-          connection.roles(
-            :tenant => tenant,
-            :user   => self)
+        def roles(tenant_id = self.tenant_id)
+          connection.list_roles_for_user_on_tenant(tenant_id, self.id).body['roles']
         end
       end # class User
     end # class OpenStack