WebSession: set cookie with new session

• In commit c1e3691cc782ecc9f641585d23024ea070ee1c8b, the statement to issue a new cookie in case of new guest user session has been removed.
  
  This was not necessary and caused guest users to miss certain session-based functionalities.
  
  Cookies are now re-issued in case of new sessions (regardless of the user being guest or not).