Fixed issue [buildoop-github-#32]

In hadoop-hdfs-datanode init script line 103 is
start_daemon -u $SVC_USER $EXEC_PATH --config "$CONF_DIR" stop $DAEMON_FLAGS

but should be the following:

if [ -n "$HADOOP_SECURE_DN_USER" ]; then
	TARGET_USER=root
else
	TARGET_USER=${HADOOP_DATANODE_USER:-hdfs}
fi
start_daemon -u $TARGET_USER $EXEC_PATH --config "$CONF_DIR" stop $DAEMON_FLAGS

The if statement control if is a secured cluster, if so it uses jsvc
which is launched by root not hdfs user