AMBARI-22472. Ambari Upgrade 2.5 -> 2.6 : Update NodeManager's HSI identity 'llap_zk_hive' and 'llap_task_hive' to use '/HIVE/HIVE_SERVER/hive_server_hive' reference instead of creating the same identity again.

*Background:*
YARN NodeManager currently has:

• 2 identities in 2.5 stack, namely : *'/HIVE/HIVE_SERVER/hive_server_hive'* and *'llap_zk_hive'*.
  • */HIVE/HIVE_SERVER/hive_server_hive* is a reference from HIVE_SERVER, whereas
  • *llap_zk_hive* creates same principal as above in a separate keytab file.

• and 3 identities in 2.6 stack:
  '/HIVE/HIVE_SERVER/hive_server_hive' and 'llap_zk_hive'.
  • */HIVE/HIVE_SERVER/hive_server_hive* is a reference from HIVE_SERVER, whereas
  • *llap_zk_hive* and *llap_task_hive* creates same principal as above in a separate keytab file.

*Issue:* Recreating same identities in different files creates issues while AMbari upgrade from 2.5 to 2.6, as the llap_zk_hive are not refreshed/updated after the upgrade. Thus, HSI fails to come up.

*Fix:*

*For HDP 2.5:* Make *llap_zk_hive* point as a reference pointing to /HIVE/HIVE_SERVER/hive_server_hive, so that we have one identity getting created only at one place and one keytab file.

*For HDP 2.6:* Make *llap_zk_hive* and *llap_task_hive* point as a reference pointing to /HIVE/HIVE_SERVER/hive_server_hive, so that we have one identity getting created only at one place and one keytab file.