We saw a case where the recovery stats reported `recovered_bytes` greater than `length_in_bytes` for one file:

```
GET /_recovery?detailed

200 OK
...
{
  "name": "_buk.fdt",
  "length_in_bytes": 26891307173,
  "reused": false,
  "recovered_in_bytes": 35324928266,
  "recovered_from_snapshot_in_bytes": 8433621093
}
...
```

NB `35324928266 == 26891307173 + 8433621093`

This causes Elasticsearch to compute a negative value for the reserved space on the target node of this recovery, which prevents stats APIs from working. This appears to be caused by a network-level failure which triggers a retry without first cancelling an ongoing download of a different file with the same name from the snapshot repository.

---

### Workaround

Restart the target node to clear these stats.
server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
* {@link ReplicationTracker#markAllocationIdAsInSync(String, long)}
     * for additional details.
     *
     * @param allocationId    the allocation ID of the shard to mark as in-sync
     * @param localCheckpoint the current local checkpoint on the shard
     */
    public void markAllocationIdAsInSync(final String allocationId, final long localCheckpoint) throws InterruptedException {
        assert assertPrimaryMode();
        replicationTracker.markAllocationIdAsInSync(allocationId, localCheckpoint);
    }
    /**
     * Returns the persisted local checkpoint for the shard.
     *
     * @return the local checkpoint
     */
    public long getLocalCheckpoint() {
        return getEngine().getPersistedLocalCheckpoint();
    }
    /**
     * Returns the global checkpoint for the shard.
     *
     * @return the global checkpoint
     */
    public long getLastKnownGlobalCheckpoint() {
        return replicationTracker.getGlobalCheckpoint();
    }
    /**
     * Returns the latest global checkpoint value that has been persisted in the underlying storage (i.e. translog's checkpoint)
     */
    public long getLastSyncedGlobalCheckpoint() {