change TestScan to insert hosts the proper way (through announcements…

… in a transaction and then mining a block with that txn) rather than through unexported addHosts method, simplify query used in addHosts because we only need to update lastAnnouncement and the net addresses for that host, use a separate query for unsuccessful scans and successful scans in addHostScans

explorer/events.go

@@ -223,6 +223,7 @@ func AppliedEvents(cs consensus.State, b types.Block, cu ChainUpdate) []Event {
 				})
 			}
 		}
+
 		addEvent(types.Hash256(txn.ID()), cs.Index.Height, &e, relevant) // transaction maturity height is the current block height
 	}