[BUGFIX] Keep session cookie if session data is present

[BUGFIX] Keep session cookie if session data is present

The AbstractUserAuthentication::checkAuthentication() method calls
the logoff() method on every failed login attempt.

Since a logoff also causes a removal of the cookie,
any (anonymous) session data will be left unaccessible.

Keep the cookie when session data is present.

Releases: 6.2
Resolves: #58713
Change-Id: I744456f62197a7278635d8564d4883564d954dd2
Reviewed-on: https://review.typo3.org/30485
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel
Reviewed-by: Wouter Wolters
Reviewed-by: Stefan Neufeind
Reviewed-by: Markus Klein
Tested-by: Markus Klein