Some plugin errors not logged/logged at debug level with Telegraf 1.12.5

[danielnelson]

Many plugin errors are not being logged at the error level and instead are being logged at debug level.

Relevant telegraf.conf:

Many configurations that will produce an error:

[[inputs.influxdb]]
  urls = ["http://wrong.local:8086/debug/vars"]

System info:

Telegraf 1.12.5

Steps to reproduce:

1. Run Telegraf with a plugin that will produce an error.

Expected behavior:

Error emitted from influxdb input due to the wrong hostname.

E! [inputs.influxdb] Error in plugin: [url=http://wrong.local:8086/debug/vars]: Get http://wrong.local:8086/debug/vars: dial tcp: lookup wrong.local: no such host

Actual behavior:

Error appears not to be logged at first, and is instead logged at debug level:

D! [inputs.influxdb] Error in plugin: [url=http://wrong.local:8086/debug/vars]: Get http://wrong.local:8086/debug/vars: dial tcp: lookup wrong.local: no such host