Error: can't get nginx-proxy container ID !

[KES777]

Add 'depends_on': nginx-proxy/acme-companion#102 (comment)
to fix this problem:

docker logs -f otm-nginx-proxy-letsencrypt-1
Info: running acme-companion version v2.2.1
Error: can't get nginx-proxy container ID !
Check that you are doing one of the following :
	- Use the --volumes-from option to mount volumes from the nginx-proxy container.
	- Set the NGINX_PROXY_CONTAINER env var on the letsencrypt-companion container to the name of the nginx-proxy container.
	- Label the nginx-proxy container to use with 'com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy'.