Delete empty backup files in advance, fall back to private ip and hostname without throwing, throw on gossip mismatch when grabbing assigned token

(#972) Throw in case of gossip mismatch when determining replace_ip in assigned token case
(#969) Make getPublicIP and getPublicHostname fail elegantly when those attributes are absent.
(#968) Delete empty incremental backup files rather than throwing when we try to rate limit them.