Bug 28263: Fix too_many auto renewal message

Bug 28263: Fix too_many auto renewal message

To test:
1. Make an item eligible for auto_renewal.
2. Set circ rule so only 1 auto_renewal is allowd.
3. Run auto_renew once, get a successful message.
4. Run it again and get the too_many error "You have reached the maximum number of checkouts possible."
5. This has nothing to do with the number of checkouts
6. Apply patch and updatedatabase.
7. Do 1-4 again.
8. Message is now "You have reached the maximum number of renewals possible."

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>