qos.cgi: Fix truncated status output

qos.cgi: Fix truncated status output

In the past only the fist line of the status output has been passed
to the cleanhtml() function and displayed. Now the whole output will be
converted to a string, cleaned and displyed on the WUI again.

Fixes #12666.

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>
Reviewed-by: Bernhard Bitsch <bbitsch@ipfire.org>
Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>