Fix issues with metric reporting (#11518)

* report active users in graphite stats

* use bus to publish system stats

* metrics: avoid using events unless we have to

this commit also changes the default interval
for updating the stats gauges. Seems like the old values
was a product of previous metrics implementation

pkg/services/sqlstore/stats.go

@@ -68,6 +68,7 @@ func GetSystemStats(query *m.GetSystemStatsQuery) error {
 	}
 
 	query.Result = &stats
+
 	return err
 }