R1:f060d8eb8fc1

Warn if daemons are not running

Summary:
Currently, we try to mostly-kind-of-work if daemons aren't running (for example, we send mail in-process). I want to stop doing this. A major motivator is that `metamta.send-immediately` is confusing for a lot of users and frequently the cause of performance problems. Increasingly, functionality of applications depends on the daemons (Harbormaster, Drydock, Nuance all require daemons to do anything at all). They're also fairly stable/robust/well-tested and no…