ospfd: Fix initial Opaque LSA DB synchronisation

ospfd: Fix initial Opaque LSA DB  synchronisation

ospfd has issues resynchronising its Opaque LSA DB with neighbours after restart
or interface events. The problem comes from opaque_lsa.c code that blocks
subsequent opaque LSA flooding until the neighbour router acknowledge that, and
removes the old opaque LSA from its LSDB. The bug comes from the fact that the
lock is never release, thus avoiding subsequent opaque LSA flooding.

More detail about the bugs and its solution is describeid in file
doc/te-link-params.md

Signed-off-by: Olivier Dugeon <olivier.dugeon@orange.com>
(cherry picked from commit 149210656045c363d8f59b97ad9251b0c06a15df)