Azure Service Bus implementation should not re-use subscriptions to topics when instances reboots (Resource Conflict Occurred)

Steps to reproduce

Previously a subscription to an Azure Service Bus topic was created when a site started and deleted when the site was stopped. If the subscription already existed on start then it would re-use that subscription (for example in a crash situation when it was not possible to remove the subscription on shutdown). The Azure Service Bus subscription name was the name of the server + IIS instance.

There is an unreproducable error situation where Azure Service bus reports "Resource Conflict Occurred". It is not possible to start the application at this point. This fix will change the behaviour and instead create globally unique subscriptions for each application and let Azure auto delete subscriptions when they are no longer being used, this avoids that subscriptions have to be re-created on application restarts.

Workaround: Delete Azure Service bus and re-create, configure new connection string in web.config.

An unconfirmed alternative approeach is re-deploying the application or re-scaling the application to move off the failing subscription / server.