Fix erroneous logging of config file changes when it hasn't changed.
Loosen DNS resolver so it caches and tries to reuse recent IPs.

As long as an IP has been seen in the past 4 hours, it will continue to
use it. This slightly breaks DNS TTL, but this was needed to accommodate
domains that have very short TTLs and cycle through a variety of IPs.
That was causing new IPs and nginx to be reloaded too frequently. 4
hours may be overkill, though, so this could be revisited if that turns
out to be too long.
Spin up a separate redis server for running tests.

Previously, it was using the main redis database that's also used in
development, so things were getting overwritten between development and
test.