HDDS-4793. Allow recon access /dbCheckpoint in ozonesecure-om-ha

[adoroszlai]

What changes were proposed in this pull request?

Add recon/recon@EXAMPLE.COM to ozone.administrators in ozonesecure-om-ha as suggested by the error message:

om1_1 | ERROR om.OMDBCheckpointServlet: Permission denied: User principal 'recon/recon@EXAMPLE.COM' does not have access to /dbCheckpoint.
om1_1 | This can happen when Ozone Manager is started with a different user.
om1_1 | Please append 'recon/recon@EXAMPLE.COM' to OM 'ozone.administrators' config and restart OM to grant current user access to this endpoint.

https://issues.apache.org/jira/browse/HDDS-4793

How was this patch tested?

cd hadoop-ozone/dist/target/ozone-1.1.0-SNAPSHOT/compose/ozonesecure-om-ha
KEEP_RUNNING=true ./test.sh
docker-compose logs om1 om2 om3 | grep Checkpoint
...
om1_1 | [...] INFO om.OMDBCheckpointServlet: Received request to obtain OM DB checkpoint snapshot
om1_1 | [...] INFO db.RDBCheckpointManager: Created checkpoint at /data/metadata/db.checkpoints/rdb_rdb_checkpoint_1612468871049 in 15 milliseconds
om1_1 | [...] INFO om.OMDBCheckpointServlet: Time taken to write the checkpoint to response output stream: 30 milliseconds
om1_1 | [...] INFO db.RocksDBCheckpoint: Cleaning up RocksDB checkpoint at /data/metadata/db.checkpoints/rdb_rdb_checkpoint_1612468871049

https://github.com/adoroszlai/hadoop-ozone/runs/1833972692

[bharatviswa504]

Thank You @adoroszlai for the contribution and for identifying the issue.

[adoroszlai]

Thanks @bharatviswa504 for reviewing and committing it.