storage.fossology_license_add: Fix one insert query too many

Prior to this commit, this ended up running twice the insertion query. First
time, on conflict actually inserting data, then running again. The second extra
time being a noop (plus costing extra time), thus returning a summary of no new
elements inserted.

The tests must be improved to actually check the insertion output. It's not the
case or it would have been caught already.