Bug 13504: Remove the '----' marker for CHECKIN and CHECKOUT notices

Bug 13504: Remove the '----' marker for CHECKIN and CHECKOUT notices

If only 1 item exist in the message, the marker is not removed.
This marker is removed by render_metadata, but this method is only
called on appending.

Test plan:
1/ Enable the CHECKIN and/or CHECKOUT notices for a patron
2/ check and item in or out and verify that the marker is no longer
displayed in the generated notices.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>