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 reasonable install should be running without them.
This will let us simplify or remove some flags (like `metamta.send-immediately`) and simplify some other processes like search indexing.
Test Plan: Stopped daemons, loaded warnings, saw daemon warning. Started daemons, reloade, no warning.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T3857
Differential Revision: https://secure.phabricator.com/D7964
