ospfd: run DR election prior to LSA regeneration

ospfd: run DR election prior to LSA regeneration

The results from DR election are used when constructing router-LSAs.
E.g. they are used to determine whether a broadcast interface should
be added with a link type of stub interface or transit interface.

Therefore, we should run DR election prior before regenerating LSAs.

Before commit c363d3861b5384a31465a72ddc3b0f6ff007a95a the DR election
was called synchronously prior to router-LSA regeneration which was run
asynchronously.

This fixes bug #761 on the Quagga bugzilla.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Acked-by: Feng Lu <lu.feng@6wind.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>