Automatic migration from InfluxDB OSS 1.8.10 to 2.1.1 fails

Hi there,

I find it particularly difficult to follow the [documentation](https://docs.influxdata.com/influxdb/v2.1/upgrade/v1-to-v2/) to upgrade from 1.x to 2.x, and even after applying the required steps, I end up with fatal error or unauthorised access.

Below is a more precise description (at least I hope so) of the error and the steps to reproduce it

Minimal actions needed to reproduce the behavior.

1. Have a InfluxDB OSS 1.8.10 up and running on a single instance
2. Apply steps described to [perform the upgrade](https://docs.influxdata.com/influxdb/v2.1/upgrade/v1-to-v2/automatic-upgrade/#perform-the-upgrade)
3. In particular use the following command to do the uprage
```
sudo -u influxdb influxd upgrade --config-file /etc/influxdb/influxdb.conf --v2-config-path /specific_path/influxdbv2/config.toml -e /specific_path/influxdbv2/engine -m /specific_path/influxdbv2/influxd.bolt -c /specific_path/influxdbv2/configs --log-path /specific_path/influxdbv2/upgrade.log --log-level debug
```
4. Start the influxDB instance (as a service or as influxd process)

__Expected behavior:__
* Have documented and precise steps to follow to perform the upgrade:
* End up with an up and running InfluxDB 2.1.1 service, with all data from 1.8.10 migrated in bucket and organisation

__Actual behavior:__
Differents errors when starting `influxd` :
* `too many files open`
* no org for default user
* Error: failed to list users: 401 Unauthorized: unauthorized access

__Environment info:__

* System info: Run Linux 5.13.0-1014-aws x86_64 20.04.1-Ubuntu
* InfluxDB version: InfluxDB v2.1.1

Start with the linked v1-to-v2 automatic-upgrade documentation and reproduce the upgrade using the provided `influxd upgrade` command on InfluxDB OSS 1.8.10. Check the reported startup errors, including `too many files open`, missing organization data, and 401 unauthorized access; done means a running InfluxDB 2.1.1 service with migrated buckets and organizations plus precise upgrade steps.

Written by the indexing model from the issue text.