Add transport check in TestMessageBus injection

It looks like the static variable testMessageBus in
AbstractSingleNodeStreamDeploymentIntegrationTests(AbstractSNSDIT) gets
a value from previously loaded test class (ex: RabbitSNSDIT) and
thereby non-null check on TestMessageBus injection fails if the class
LocalSNSDIT is loaded after RabbitSNSDIT. Hence, added an additional
check to verify if the transport is local as it is LocalSNSDIT that
doesn't set the testMessageBus.