* Two things:
* Change how we populate and clear leader UUID. This fixes a case where
if a standby disconnects from an active node and reconnects, without the
active node restarting, the UUID doesn't change so triggers on a new
active node don't get run.
* Add a bunch of test helpers and minor updates to things.
The result will still pass gofmtcheck and won't trigger additional
changes if someone isn't using goimports, but it will avoid the
piecemeal imports changes we've been seeing.