message: Change default nmix
diff: AliAnalysisTaskXi1530* AddTaskXi1530(const char *taskname = "Xi1530"
  , const char *option = "SYS"
  - , int nmix=20
  + , int nmix=10
  , const char* suffix = "MB")
  {
  AliAnalysisManager *mgr = AliAnalysisManager::GetAnalysisManager();
  