Disable spamassasin

[MooCloud_Matt]

For those cloudron installs that use external spam filtering/gateway, the extra latency/resources that haraka use to process every email are wasted because that email has already been processed by an antispam.

it would be a really great feature to be able to disable SA check.

For now it's possible but not permanent, because the Harake config files are not save in the filesystem,