Added IF NOT EXISTS to custom buffer sql scripts.

Avoids problems with l2j-server-cli.

src/main/resources/sql/custom/custom_buffer_service_1_ulists.sql

-CREATE TABLE `custom_buffer_service_ulists` (
+CREATE TABLE IF NOT EXISTS `custom_buffer_service_ulists` (
   `ulist_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
   `ulist_char_id` int(10) unsigned NOT NULL,
   `ulist_name` varchar(255) NOT NULL,

src/main/resources/sql/custom/custom_buffer_service_2_ulist_buffs.sql

-CREATE TABLE `custom_buffer_service_ulist_buffs` (
+CREATE TABLE IF NOT EXISTS `custom_buffer_service_ulist_buffs` (
   `ulist_id` int(10) unsigned NOT NULL,
   `ulist_buff_ident` varchar(255) NOT NULL,
   PRIMARY KEY (`ulist_id`,`ulist_buff_ident`),