More refactors for EventRepository

- rename methods to use the works 'record' instance of 'create'. We may
need to make special methods for create and delete events; using the
word 'record' will make these new methods less confusing.

- calls to record methods pass a symbol specifying only the action,
  instead of the whole type string
Return proper error codes for deleting service_instances

- 404 when instnace not found
- 403 when user not authorized to delete

This fixes a regression introduced in
3a0590b61f832787dc0eeb19c9407dfcde2a8cc7
Store request_addrs as controller instance variable for service_instance update

This fixes a regression introduced in a recent story