Local ansible connection is required to use env vars

[jaywcarman]

In order to use a local environment variable to set options like ibmcloud_api_key (env IC_API_KEY) or region (env IC_REGION) the target host must be using a local Ansible connection (e.g. localhost ansible_connection=local). This behavior is inherent to using env_fallback in Ansible module arguments (see Ansible Argument spec), but is not clearly documented in our modules or examples.

Initial documentation is here in this issue :) but would be preferable about update example READMEs.

Thanks to @bmcsheehy for bringing this up.