ospfd: make ospf_maxage_lsa_remover actually yield

ospf_maxage_lsa_remover whould check whether to yield,
but run on anyway.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Signed-off-by: David Lamparter <equinox@diac24.net>
ospfd: fix flooding procedure

An ospf router should accept a new maxage LSA into its lsdb if it has any
neighbors in state Exchange or Loading. ospfd would however only account
for neighbors on the same interface which does not seem to be a valid
optimization.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Signed-off-by: David Lamparter <equinox@diac24.net>