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
logger.debug("submitting async roll translog generation request");
                    final AbstractRunnable roll = new AbstractRunnable() {
                        @Override
                        public void onFailure(final Exception e) {
                            if (state != IndexShardState.CLOSED) {
                                logger.warn("failed to roll translog generation", e);
                            }
                        }
                        @Override
                        protected void doRun() {
                            rollTranslogGeneration();
                        }
                        @Override
                        public void onAfter() {
                            flushOrRollRunning.compareAndSet(true, false);
                            afterWriteOperation();
                        }
                    };
                    threadPool.executor(ThreadPool.Names.FLUSH).execute(roll);
                } else {
                    flushOrRollRunning.compareAndSet(true, false);
                }
            }
        }
    }
    /**
     * Build {@linkplain RefreshListeners} for this shard.
     */
    private RefreshListeners buildRefreshListeners() {
        return new RefreshListeners(