Fix failure on OBJ plugin when CLI is not configured

[zliang-akamai]

📝 Description

This is to fix an issue that prevent OBJ plugin to work when no default user has been configured to the CLI.

✔️ How to Test

1. Remove existing CLI configuration file: rm ~/.config/linode-cli (if you have important stuff in the config, please back it up rather than remove)
2. Configure CLI via environmental variables.

export LINODE_CLI_TOKEN=[YOUR_API_TOKEN]
export LINODE_CLI_OBJ_ACCESS_KEY=[YOUR_OBJ_ACCESS_KEY]
export LINODE_CLI_OBJ_SECRET_KEY=[YOUR_OBJ_SECRET_KEY]

3. Verify the OBJ plugin is still working: linode obj la