[smengcl]

Generated-by: Claude Code (Opus 5.5)

What changes were proposed in this pull request?

Addendum to #11563, following the review discussion there.

#11563 kept Recon's candidate dir after a failed OM DB download and guarded it with a Recon only untarContentsOfTarball override that extracts through .tmp files, so the retry could skip files already received. The OM follower does not do this: OzoneManager#installSnapshotFromLeader deletes the candidate dir after a failed download. Recon gets the active DB as one tarball, so the exclude list only has entries on a retry after a failure, and that saves little (only files before the cut, which compaction may make stale, and a full disk stays full).

This patch aligns Recon with the OM follower:

• Clear the candidate dir in the failure path of OzoneManagerServiceProviderImpl#getOzoneManagerDBSnapshot via RDBSnapshotProvider#init, which also resets the pinned leader.
• Remove the untarContentsOfTarball override from ReconRDBSnapshotProvider and make the base method private again.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-16880

How was this patch tested?

testPartiallyUntarredFileNotReportedOnRetry is renamed to testCandidateDirClearedAfterFailedDownload and now checks that, after a download whose tar ends in the middle of an SST file, the candidate dir is empty and the retry sends an empty exclude list.

TestOzoneManagerServiceProviderImpl, TestReconRDBSnapshotProvider, TestTriggerDBSyncEndpoint and TestRDBSnapshotProvider pass (24 tests). Checkstyle is clean.

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[sadanand48]

LGTM based on the discussions in #11563

[smengcl]

Thanks @sadanand48 for the review.