sms_queue: Make deletion of messages from DB VTY-configurable

This introduces some VTY settings that determine if delivered
or expired messages should be removed from he SQL database or not.

Change-Id: Id6174875d5c01c40d987077651b27ae1acbcaa93
diff --git a/tests/test_nodes.vty b/tests/test_nodes.vty
index a67f202..ac3ff16 100644
--- a/tests/test_nodes.vty
+++ b/tests/test_nodes.vty
@@ -181,6 +181,8 @@
 smsc
  queue max-pending 20
  queue max-failure 1
+ database delete-delivered 1
+ database delete-expired 1
 end
 
 OsmoMSC# configure terminal