Don't print Sending EDU if there is noone to send to
The logs had a lot of:
```
Sending EDU event                             destinations="[]" edu_type=m.typing
```
Which is useless if it isn't actually sending the event anywhere (destinations is empty).
MODIFY
federationsender/queue/queue.go
federationsender/queue/queue.go
@@ -96,9 +96,11 @@ func (oqs *OutgoingQueues) SendEDU(
// Remove our own server from the list of destinations.
destinations = filterDestinations(oqs.origin, destinations)
+ if len(destinations) > 0 {
log.WithFields(log.Fields{
"destinations": destinations, "edu_type": e.Type,
}).Info("Sending EDU event")
+ }
oqs.queuesMutex.Lock()
defer oqs.queuesMutex.Unlock()

Don't print Sending EDU if there is noone to send to (#721)

The logs had a lot of:

```
Sending EDU event                             destinations="[]" edu_type=m.typing
```

Which is useless if it isn't actually sending the event anywhere (destinations is empty).