Bug 8178 - circ/circulation.pl under plack duplicates checkout rows

Bug 8178 - circ/circulation.pl under plack duplicates checkout rows

Bug 7851 introduced our scoping for vairables, unfortunatly it has
side-effect that checkout rows accumulate on page reloads instead
of being initialized to empty array (which this patch fixes)

This also fixes %renew_failed initialization on each request.

Test scenario:
1. start intranet under plack
2. open /cgi-bin/koha/circ/circulation.pl and reload page few time
   confirming that rows gets duplicated
3. apply patch and reload page to verify that it works

Signed-off-by: Alex Arnaud <alex.arnaud@biblibre.com>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>