Merge branch 'master' into 2895-no-more-redis

diff --cc services/api/app/controllers/arvados/v1/users_controller.rb
index 781bd882e72e28947acd09ac5a759db3a0625496,7311deb3860c9337914ea10fe3122dfad62bdad4..a67180912345331ce8872eb7b6fce16119a160b6
--- 1/services/api/app/controllers/arvados/v1/users_controller.rb
--- 2/services/api/app/controllers/arvados/v1/users_controller.rb
+++ b/services/api/app/controllers/arvados/v1/users_controller.rb
@@@ -1,8 -1,10 +1,10 @@@
  class Arvados::V1::UsersController < ApplicationController
+   accept_attribute_as_json :prefs, Hash
+ 
    skip_before_filter :find_object_by_uuid, only:
 -    [:activate, :event_stream, :current, :system, :setup]
 +    [:activate, :current, :system, :setup]
    skip_before_filter :render_404_if_no_object, only:
 -    [:activate, :event_stream, :current, :system, :setup]
 +    [:activate, :current, :system, :setup]
    before_filter :admin_required, only: [:setup, :unsetup]
  
    def current