Bug 27860: Fix self-registration if messages with incorrect email are inqueued

If the pref KohaAdminEmailAddress was not set correctly (invalid email)
and has been used to generate message, the message_queue table can contain
some messages that are not sent (pending) and will be processed each
time a new self-reg is done.
The PatronSelfRegistrationVerifyByEmail feature must send only the
notice we just generated, not the whole pending queue.

Test plan:
1. Do not apply the patches
2. Set KohaAdminEmailAddress to an invalid email (root@localhost for
instance)
3. Turn on PatronSelfRegistrationVerifyByEmail
4. Self-reg a patron
5. Boom (that must be fixed on a separate bug report)
6. Set KohaAdminEmailAddress to a valid email (root@example.org)
7. Self-reg a patron
8. Still Boom! (because it's processing the first invalid email)
9. Apply the patches, restart_all
10. Self-reg a patron
=> The email is sent!
Notice the change in DB, the first email is still there with status
"pending" and second email is sent!

QA: at step 10. TODO first email must be 'failed' (highlight in tests)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

opac/opac-memberentry.pl

@@ -197,7 +197,7 @@ if ( $action eq 'create' ) {
                 },
             );
 
-            C4::Letters::EnqueueLetter(
+            my $message_id = C4::Letters::EnqueueLetter(
                 {
                     letter                 => $letter,
                     message_transport_type => 'email',
@@ -206,9 +206,7 @@ if ( $action eq 'create' ) {
                       C4::Context->preference('KohaAdminEmailAddress'),
                 }
             );
-            my $num_letters_attempted = C4::Letters::SendQueuedMessages( {
-                    letter_code => 'OPAC_REG_VERIFY'
-                    } );
+            C4::Letters::SendQueuedMessages({ message_id => $message_id });
         }
         else {
             ( $template, $borrowernumber, $cookie ) = get_template_and_user(