Bug 18497: Use report id to retrieve saved SQL instead of passing param

Bug 18497: Use report id to retrieve saved SQL instead of passing param

This patch takes some of the code when executing report and moves it to
a sub to be reused when downloading

To test:
1 - Run some very long report (see comment #1)
2 - Try to download, erk!
3 - Apply patch
4 - Run report, results hould not have changed
5 - Try to download, success!
6 - Ensure reports work as before

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>