[BUGFIX] Prevent double loading of session data

At the moment we load the session data to verify authentication and
again to verify session existence. This isn't necessary. Also removing
the session deletion if we didn't find session data.

Resolves: #53598
Releases: 6.2
Change-Id: Ibc3c4ebc5c1bbca970374172f714bddcd37b539a
Reviewed-on: https://review.typo3.org/25510
Reviewed-by: Thorsten Kahler
Tested-by: Thorsten Kahler
Reviewed-by: Wouter Wolters
Reviewed-by: Michiel Roos
Tested-by: Michiel Roos
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind
Reviewed-by: Ernesto Baschny
Tested-by: Ernesto Baschny