ospf6d: don't create Adv-ID:0.0.0.0 LSAs at start

ospf6d: don't create Adv-ID:0.0.0.0 LSAs at start

When ospf6d comes up, it gets interface and address state before it
decides on its router ID.  This results in a bunch of LSAs with
advertising router ID 0.0.0.0 in the LSDB.  Not quite right.

There's a whole bunch of paths leading to this, so just drop the LSA in
ospf6_lsa_originate.  The router-ID change causes everything to be
readvertised anyway (... but the delete doesn't catch the 0.0.0.0 stuff
because the router-ID is now different.)

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>