FELIX-6815 Fix race condition for defaultBaseUrl

[ghenzler]

No description provided.

[cziegeler]

You could use the service reference from the service event directly to avoid reaching out to the service registry again.
Maybe we could also use a DS service reference with a target filter instead and bind/unbind methods. That should simplify the code

[laeubi]

Instead of a raw service listener I would use a ServiceTracker instead what has a method getTracked() what gives you both the service and the servicereference to check the properties from or you use a customizer that holds the interesting properties in an AtomicReference.

[cziegeler]

As this is a DS component, it is better to use DS features for service tracking, instead of going to low level framework mechanisms. (and I know I initially suggested ServiceListener, which should have been a @reference from the start)