make sure function exists before executing

#bug551
http://platform.dandigbib.org/issues/551

For some reason reservation.inc was not included when handling ILL loans. Probably because ting client throws an exception like this one:
'Unexpected error message in response'
that one comes from opensearch:
'"Error: unknown/missing record: 870970-basis:575023933V"
and that one comes from the V appended to the pid. That can happen in the local system.

the second change is due to the fact that the $orders array was not iterated correctly and threw an assfull of warnings. It comes in the form :
$orders [ ready_for_pickup ] [ 08-10-2014 15:35:02 ] [ DingProviderReservation ]
The files array is a class loader, and is only loaded if the file contains a class or interface. Reservation.inc is loaded from ding_provider, but as it throws an exception ...