Bug 15705: Reset the last error when an auto renew successes

Bug 15705: Reset the last error when an auto renew successes

The auto_renew_error has to be reset when an auto renew successes,
otherwise the patron is not going to receive the correct notice.

Test plan;
- Checkin an item and mark it as auto renewal (specify a due date in the past to allow auto renewals)
- Set OPACFineNoRenewalsBlockAutoRenew to 'Block' and 'OPACFineNoRenewals' to '1'
- Execute the script
=> Auto renewed, column auto_renew_error is null
- Add a fine of '2' to the patron
- Execute the script
=> Not auto renewed, column auto_renew_error is 'auto_too_much_oweing'
=> On the interface youo see the correct message "Automatic renewal failed, patron has unpaid fines"
- Pay the fine
- Execute the script

Without this patch the auto_renew_error is not reset and the patron is going to
receive a letter telling him he own too much money to the library
With this patch the patron will receive a letter to inform him the renew has been done!

Signed-off-by: Jonathan Field <jonathan.field@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>