Bug 20695: Fix multiple upload result in tools/upload script

Bug 20695: Fix multiple upload result in tools/upload script

Instead of calling UploadedFiles->find only once with $id, we should
extract all comma separated id's from the parameter.

Test plan:
[1] Before this patch, upload two files at once in Tools/Upload. After doing
    so, you should see only one result reported. But both files should
    have been uploaded.
[2] With this patch, repeat step 1 and see two upload results.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Patch applies and functions as described.
Signed-off-by: Dilan Johnpullé <dilan@calyx.net.au>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>