BUG/MINOR: log: The log of quotted capture header has been terminated by 2 quotes.

Julien Vehent repport that the log format '%{+Q}hr' display the value
termnated by two chars '"' like this: '"value""'. This patch just remove
the second quote.

This bug is old but 1.5-specific but users of older 1.5 versions may be
interested in a backport.