influxd upgrade may unintentionally destroy data

[qbasicer]

Steps to reproduce:
List the minimal actions needed to reproduce the behavior.

1. Upgrade from 1.8.x to 2.x on Arch Linux
2. Observe that the upgrade did not actually occur properly
3. Attempt upgrade influxd upgrade -m 'pwd' -b primary --config-file /etc/influxdb/influxdb.conf.pacsave -o default --overwrite-existing-v2 from /var/lib (pwd is in backticks)
4. Observe that /var/lib is now empty

Expected behavior:
An error describing what is about to be wiped is not actually a boltdb

Actual behavior:
/var/lib is now empty

Environment info:

• System info: Linux 5.11.4-arch1-1 x86_64
• InfluxDB version: InfluxDB 2.0.4 (git: 4e7a59b) build_date: 2021-03-12T20:26:21Z
• Other relevant environment details: Arch Linux

Config:
N/A