TTL mismatch handling
Checking TTL mismatches in RRSets. In some cases a TTL mismatch should lead to fatal error and refusing to load/accept zone, in others it should only trigger a warning:
- master zone load: refuse to load the zone, log error
- incoming UPDATE: refuse the UPDATE, log error
- slave zone load (from disk): load the zone, log warning
- incoming [A,I]XFR (slave): accept, but log warning
Currently it always logs the message as warning. To distinguish between warning and (fatal) errors would require minor modification of semantic check errors. @jkadlec should do that.
TESTS:
- I've added tests for zone load on master and slave.
- Tests for [A,I]XFR and UPDATEs will be done by @dsalzman