update-ids-ruleset: Silent script if no providers settings file exists.

update-ids-ruleset: Silent script if no providers settings file exists.

Only try to read-in the providers settings file, in case it exists.
Otherwise the script produces an error message, about the missing file,
each time it gets executed.

Because of the fcron job this would be twice a day in most cases.

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>
Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>