ospfd: Compile fix for opaque support

ospfd: Compile fix for opaque support

* ospfd: Refresher logic cleanup broke OSPF opaque, which does its own thing
  with regard to refresher logic and which also, in the protocol, requires
  implementations to keep state of which OI an LSA is received on (rather
  than providing information in the LSA to allow it to be looked up - as
  other LSAs requiring such assocation were careful to do).
* ospf_lsa.h: (struct ospf_interface) Add back the pointer to oi, but only
  for type-9 now.
* ospf_nsm.c: (ospf_db_summary_add) check the oi actually exists first -
  doesn't obviate the need for opaque to ensure oi pointers get cleaned up
  when ospf_interfaces disappear.
* ospf_opaque.{c,h}: (ospf_opaque_functab,ospf_opaque_lsa_refresh) Refresher
  LSA functions now need to return the LSA to the general refresh logic,
  to indicate whether the LSA was refreshed.