EventHubs: if received message does not have trace context, spans are not created

[lmolkova]

Describe the bug
If EventHubs message does not have diagnositc-id in properties, spans are not created

azure-sdk-for-java/sdk/eventhubs/azure-messaging-eventhubs/src/main/java/com/azure/messaging/eventhubs/PartitionPumpManager.java

Line 370 in f48ebe8

return Context.NONE;

To Reproduce
Send event from non-instrumented producer

Code Snippet
e.g. eventhub spring binder

	@Bean
	public Consumer<Message<String>> consume() {
		return message -> { .. }
        }

Expected behavior
Process span should be created regardless of diagnosticId is present or not (as you might want to monitor consumer even if you don't own or monitor producer)