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/indices/recovery/RecoveryState.java
protected long startTime = 0;
        protected long startNanoTime = 0;
        protected long time = -1;
        protected long stopTime = 0;
        public Timer() {}
        public Timer(StreamInput in) throws IOException {
            startTime = in.readVLong();
            startNanoTime = in.readVLong();
            stopTime = in.readVLong();
            time = in.readVLong();
        }
        @Override
        public synchronized void writeTo(StreamOutput out) throws IOException {
            out.writeVLong(startTime);
            out.writeVLong(startNanoTime);
            out.writeVLong(stopTime);
            
            out.writeVLong(time());
        }
        public synchronized void start() {
            assert startTime == 0 : "already started";
            startTime = System.currentTimeMillis();
            startNanoTime = System.nanoTime();
        }
        
        public synchronized long startTime() {
            return startTime;
        }
        
        public synchronized long time() {