[BUGFIX] Functional tests cannot write to backend log

Functional test cases cannot write to the backend log. The
log entry also has an information about the currently used
IP address, which is taken from the environment variable
REMOTE_ADDR. In a CLI disposal this value is NULL and cannot
be stored in the database, since the accordant sys_log.IP
field does not support NULL values.

Fixes: #54849
Releases: 6.2
Change-Id: If6c572c62ab7022a4cab596fa4660dec754aee3c
Reviewed-on: https://review.typo3.org/26697
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters