[BUG] CLI disregards --config and fails

[alexgmathews]

Steps To Reproduce

1. Operating System: Debian 12 x86_64
2. Vultr-CLI Binary: vultr-cli_v3.4.0_linux_amd64 installed to /usr/local/sbin/vultr-cli with owner/group root:root and permissions 700
3. Configuration file placed at /etc/vultr-cli.yaml with contents api-key: 123XYZ... with owner/group root:root and permissions 600
4. Shell Environment: bash, root user (command executed directly as root / not prefixed by sudo)
5. Command: $ vultr-cli account --config /etc/vultr-cli.yaml

Error Message

Error Reading in file: /root/.vultr-cli.yaml
Error:
Please export your VULTR API key as an environment variable or add 'api-key' to your config file, eg:
export VULTR_API_KEY='<api_key_from_vultr_account>'

Expected behavior
If the --config flag is defined...

1. vultr-cli should use the defined path for configuration
2. vultr-cli should not attempt reading $HOME/.vultr-cli.yaml
3. the error message should give an example demonstrating add 'api-key' to your config file

[optik-aper]

Relates to #478