Fix MariaDB dbimport: utf8mb4 collation and dbimport.conf

Use utf8mb4_unicode_ci in base SQL (MariaDB lacks utf8mb4_0900_ai_ci).
Add Updates.ExceptionShutdownDelay to dbimport.conf.dist to match
DBUpdater expectations.

data/sql/base/db_world/player_shapeshift_model.sql

@@ -27,7 +27,7 @@ CREATE TABLE `player_shapeshift_model` (
   `GenderID` tinyint unsigned NOT NULL,
   `ModelID` int unsigned NOT NULL,
   PRIMARY KEY (`ShapeshiftID`,`RaceID`,`CustomizationID`,`GenderID`)
-) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci PACK_KEYS=0;
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci PACK_KEYS=0;
 /*!40101 SET character_set_client = @saved_cs_client */;
 
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