As a user, I want to be able to detect when a network function is removed

Acceptance Criteria

Event is received when an NF is removed

xNF is removed from the filtered list in each subscription

NOTE: we may not remove the NF from the filtered list when the NF is removed from the network, filtered list will be stored in consul and we probably wont be able to edit this, in that case, the list would remain unchanged and this story would not be required. if the NF was added back in at a later date, the subscription would be reapplied since the NF would still be present in the filtered list.