[master] complete NTA work

3882.	[func]		By default, negative trust anchors will be tested
			periodically to see whether data below them can be
			validated, and if so, they will be allowed to
			expire early. The "rndc nta -force" option
			overrides this behvaior.  The default NTA lifetime
			and the recheck frequency can be configured by the
			"nta-lifetime" and "nta-recheck" options. [RT #36146]

lib/dns/cache.c

@@ -300,6 +300,8 @@ dns_cache_create3(isc_mem_t *cmctx, isc_mem_t *hmctx, isc_taskmgr_t *taskmgr,
 		result = isc_task_create(taskmgr, 1, &dbtask);
 		if (result != ISC_R_SUCCESS)
 			goto cleanup_db;
+
+		isc_task_setname(dbtask, "cache_dbtask", NULL);
 		dns_db_settask(cache->db, dbtask);
 		isc_task_detach(&dbtask);
 	}