This allows testing of the configuration before one will try to restart
dnsdist with a broken config. Additionally, add tests to confirm the
config check still works.
dnsdist: Explicitly use python2 for tests
dnsdist: add --check-config commandline switch
-c is --client
Just one thing, setupLua() outputs a warning but does not throw an exception if the configuration file does not exist. I believe that's fine, but that means we will gladly validate a non-existent file, which might not be what you had in mind.
An empty config is a valid config was my reasoning :)