Update L70ETC concert mobs to work in instances (normal difficulty)

This is required because this event can take place in BRD instance

Basicly this is UPDATE creature_ai_scripts SET event_flags=event_flags|2 WHERE creature_id IN "LCT concert troup" ;

Based on bug-report by Jethrogibbs in http://www.scriptdev2.com/threads/6058-error-server-log

This will expect (but might work already without) CMaNGOS commit [12378]