Failure scenario: Test 'rw-core' crash

Once VOLTHA is operational (working) if the single member of a r/w core pair that is currently handling requests crashes then any in-flight requests should return an error and all pending requests should be routed to the other member of the pair, which in turn should become the active member of the pair. When the crashed r/w core is restarted it should come back as the standby member of the pair.