* Remove syntax error
When evaluated (i.e. when nginx_amplify_enable=true and
nginx_amplify_api_key is defined) this line causes a syntax error
To check for empty string, opted for temporary solution outlined in https://github.com/ansible/ansible-lint/issues/457
* Fix reference to amplify api key
Previously was labelled `amplify_api_key`. Changed to
`nginx_amplify_api_key` in #a55a50d
* Fix reference to default config file
On my system at least (bionic), the default configuration file is
`/etc/amplify-agent/agent.conf.default`
This is also assumed be to the case on the amplify install shell script https://github.com/nginxinc/nginx-amplify-agent/blob/master/packages/install.sh#L526
a7d3164ba1