Use getaddrinfo instead of gethostbyname for thread safety
Use getaddrinfo instead of gethostbyname for thread safety

dmlc/rabit,dmlc/xgboost,dmlc/rabit,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/rabit,dmlc/xgboost,dmlc/xgboost,dmlc/rabit