Bug 18990: Overdue Notices are not sending through SMS correctly

Bug 18990: Overdue Notices are not sending through SMS correctly

Bug 18478 fixed sms via email problems under the assumption that
to_address was either smsalertnumber or blank.

It seems overdues set the to_address to email. This patch changes the
code to enforce that an sms sent with emial driver will use the
smsalertnumebr and provider defined for the borrower, regardless of what
is set in the queue

To test:
 1 - Define a messaging prefs for a patron to recieve hold notices via
  SMS
 2 - Ensure you have defined an SMS message for an overdue letter
 3 - Set an SMS alert number for patron
 4 - Set the SMS::Send driver to 'Email'
 5 - Checkout an item as overdue to trigger notice above
 6 - Run overdue_notices.pl
 6 - Check the db and note the address is email
 7 - run process_message_queue.pl
 8 - Check db - address is email followed by service provider
 9 - Apply patch
 10 - repeat
 11 - Message to_address should be populated with smsalertnumber

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>