BUG/MINOR: cfgparse-listen: fix option httpslog override warning message

BUG/MINOR: cfgparse-listen: fix option httpslog override warning message

"option httpslog" override warning messaged used to be reported as
"option httplog", probably as a result of copy paste without adjusting
the context. Let's fix that to prevent emitting confusing warning messages

The issue exists since 98b930d ("MINOR: ssl: Define a default https log
format"), thus it should be backported up to 2.6

(cherry picked from commit 17e52c922b577e1b677098b34e47cd0a85f31e8b)
Signed-off-by: Willy Tarreau <w@1wt.eu>