Bug 2389: Add --test switch to overdue_notices.pl

Bug 2389: Add --test switch to overdue_notices.pl

This patch adds the --test option switch to the overdue_notices.pl script
so it can be ran without doing any actual action.

To test:
- Have a patron with overdue items (simulate a checkout for a past date. Note it implies
  that the circ rules are defined so the patron is overdue)
- Run:
  $ sudo koha-shell kohadev
  koha-dev$ misc/cronjobs/overdue_notices.pl --test
=> SUCCESS: The script is ran but the patron isn't debarred and no notice messages are queued.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Barton Chittenden <barton@bywatersolutions.com>
Signed-off-by: Katrin Fischer  <katrin.fischer@bsz-bw.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>