Bug 16280: purge_suggestions.pl: Cron job log should tell number of days used

Bug 16280: purge_suggestions.pl: Cron job log should tell number of days used

To test:
- Apply patch
- Set syspref CronjobLog to "Log"
- Set syspref PurgeSuggestionsOlderThan e.g. to 20
- From console, run misc/cronjobs/purge_suggestions.pl
- Check entry in cgi-bin/koha/admin/preferences.pl?op=search&searchfield=log
- Verify that log entry contains number of days (20, same as in syspref)
- From console, run misc/cronjobs/purge_suggestions.pl -days 100
- Verify that log entry contains number of days (100, same as in param -days)

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>