[BUGFIX] LDAP search filter is not stripped

Fixes: #60440
Change-Id: I63d83aab5563e50b069978ebcb561df68738d2f9
Reviewed-on: https://review.typo3.org/31713
Reviewed-by: Mario Rimann <typo3-coding@rimann.org>
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>