System info:

HP iLO 4 ProLiant
Firmware Version 2.73
Telegraf 1.15.2 (git: HEAD cd037b4) on CentOS 7

Steps to reproduce:

1. Following documentation, configure Redfish plugin with HP iLO details.
   Skipping chain & host verification:
   insecure_skip_verify = true
   Setting system id:
   computer_system_id="1"

2. Running Telegraf in test mode:
   telegraf --debug --test

Expected behavior:

connection and redfish data collection.

Actual behavior:

[inputs.redfish] Error in plugin: error parsing input: invalid character '<' looking for beginning of value

Additional info:

Looks like json.Unmarshal is failing to parse the response.
running curl with same url: https://serverIP/redfish/v1/systems/1 -i --insecure -u user:"pass" -L
generates response starting with
{"@odata.context":"/redfish/v1/$metadata#Systems/Members/$entity","@odata.id":"/redfish/v1/Systems/1/",
preceded by metadata.