1. Fix OSPF opaque LSA processing to preserve the stale opaque
LSAs in the Link State Database for 60 seconds consistent with
what is done for other LSA types.
2. Add a topotest that tests for cases where ospfd is restarted
and a stale OSPF opaque LSA exists in the OSPF routing domain
both when the LSA is purged and when the LSA is reoriginagted
with a more recent instance.
Signed-off-by: Acee <aceelindem@gmail.com>
