fix db:initial_setup for creating admin account

refs #CNVS-26056

Change-Id: Ie39dc69cf742865de89ebafcb026a7b522ce4ca0
Reviewed-on: https://gerrit.instructure.com/84187
Tested-by: Jenkins
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>

app/models/role.rb

@@ -131,6 +131,10 @@ class Role < ActiveRecord::Base
     @built_in_roles_by_id[shard.id] ||= built_in_roles(reload, shard).index_by(&:id)
   end
 
+  def self.clear_built_in_roles!
+    @built_in_roles.clear if @built_in_roles
+  end
+
   def self.built_in_course_roles
     built_in_roles.select{|role| role.course_role?}
   end

lib/tasks/db_load_data.rake

@@ -129,6 +129,7 @@ namespace :db do
           raise pseudonym.errors.full_messages.first if pseudonym.errors.size > 0
           raise "unknown error saving password"
         end
+        Role.clear_built_in_roles!
         Account.site_admin.account_users.where(user_id: user, role_id: Role.get_built_in_role('AccountAdmin')).first_or_create!
         Account.default.account_users.where(user_id: user, role_id: Role.get_built_in_role('AccountAdmin')).first_or_create!
         user