[realname]Hotfix realname cookies

Closes #314

background

visitor_id is not exist since the visitor_id is born after submit in register page.

so I add the jh_gitlab_session at the very beginning of the rails starting and using it as visitor_id_code, see it initializes in jh/config/initializers/jh_session_store.rb

using _gitlab_session instead to keep minimal change.