In regtest, generateblocks returns status:BUSY if using --no-sync
I can generate blocks just fine when running a regtest node like this:

`monerod --non-interactive --regtest --keep-fakechain --offline --fixed-difficulty=1 --data-dir=/monero/data --log-file=/monero/logs/monerod.log --rpc-bind-ip=0.0.0.0 --rpc-bind-port=18551 --confirm-external-bind --log-level=2 --rpc-login="monero:monero" --disable-rpc-ban --db-sync-mode=safe --no-zmq`

But as soon as I add `--no-sync`, calls to `generateblocks` would return:

```json
{
  "id": "generateblocks",
  "jsonrpc": "2.0",
  "result": {
    "height": 0,
    "status": "BUSY",
    "untrusted": false
  }
}
```

`v0.18.3.1`