ci: download hadoop-2.8.4.tar.gz during release building for unit tests once third-parties have changed

[empiredan]

This PR is to fix https://github.com/apache/incubator-pegasus/issues/1164. Once third-parties have changed, image will not be used thus hadoop-2.8.4.tar.gz should be downloaded.

On the other hand, an error was reported as:

This told that source should be used since it will quit from return rather than exit, as following code in config_hdfs.sh:

export HADOOP_HOME="${HADOOP_HOME:-${PEGASUS_HADOOP_HOME}}"
if [ ! -d "$HADOOP_HOME/etc/hadoop" ] || [ ! -d "$HADOOP_HOME/share/hadoop" ]; then
  echo "HADOOP_HOME must be set to the location of your Hadoop jars and core-site.xml."
  return 1
fi

Thus in lint_and_test_cpp.yaml, source ./scripts/config_hdfs.sh should be used instead of ./scripts/config_hdfs.sh.