sms: Make default SMS validity period configurable via VTY

Change-Id: Ie2c81c1d5795dd9aaf07b9766013f20b01abc762
diff --git a/src/libmsc/sms_queue.c b/src/libmsc/sms_queue.c
index 7d1860f..24811c5 100644
--- a/src/libmsc/sms_queue.c
+++ b/src/libmsc/sms_queue.c
@@ -474,6 +474,7 @@
 	sqcfg->max_fail = 1;
 	sqcfg->delete_delivered = true;
 	sqcfg->delete_expired = true;
+	sqcfg->default_validity_mins = 7 * 24 * 60; /* 7 days */
 	sqcfg->db_file_path = talloc_strdup(ctx, SMS_DEFAULT_DB_FILE_PATH);
 
 	return sqcfg;