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
public static final int UNKNOWN = -1;
        private int recovered;
        private int total = UNKNOWN;
        private int totalOnStart = UNKNOWN;
        private int totalLocal = UNKNOWN;
        public Translog() {}
        public Translog(StreamInput in) throws IOException {
            super(in);
            recovered = in.readVInt();
            total = in.readVInt();
            totalOnStart = in.readVInt();
            totalLocal = in.readVInt();
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            super.writeTo(out);
            synchronized (this) {
                out.writeVInt(recovered);
                out.writeVInt(total);
                out.writeVInt(totalOnStart);