Include whitelist_clients.local in postgrey setup from config folder

[nueaf]

Copies whitelist_clients.local from config dir to /etc/postgrey.
Test is made by communicating directly with postgrey via nc on port 10023 in order to test for the correct client_name instead of localhost.

Credit for that solution to this blog post: http://www.brandonchecketts.com/archives/manually-testing-postgrey-through-a-telnet-session

[tomav]

Thanks @nueaf

[kortenkamp]

This leads to
mail | cp: cannot stat '/tmp/docker-mailserver/whitelist_clients.local': No such file or directory
on startup if there is no whitelist_clients.local file. After updating to the latest image my server seems to no longer accept mail – while investigating the reason I found this.

[nueaf]

Sorry about that. I will add a check to see if the file exists before trying to copy it.