tests: ospfapi: fix non-determinism in test

tests: ospfapi: fix non-determinism in test

fixes #13584

The test had the ospf client injecting multiple opaque LSAs on 5s pace,
but the test itself verified and advanced on an LSA in the middle of
that sequence and not the last one. Then the test reset the ospf client
and originating router. If a later injected LSA managed to get in to the
router and flooded prior to the client/router reset then the opaque data
or sequence number could differ from the expected value.

Signed-off-by: Christian Hopps <chopps@labn.net>