Add HDFS core-site.xml to the config mount

[Jimvin]

We currently add hdfs-site.xml to the config mount, but not core-site.xml. This would be useful since it completes the Hadoop HDFS client configuration and allows for debugging by connecting to HDFS from the Hive pod. Without this you receive an error message, "Exception in thread "main" java.lang.RuntimeException: core-site.xml not found." This can be taken from the same HDFS configMap that hdfs-site.xml uses.

[zaultooz]

Adding the core-site.xml would also ensure that hive defaults to using the HDFS cluster as default when creating schemas / tables.