tests: Modify topotests to include write-multiplier config

tests: Modify topotests to include write-multiplier config

Modify both the default and vrf ospf6 topologies to include a test
where write-multiplier is configured to a non-default value and
the ospf6 neighbors are reset then checked.
Run black on both test files.

Signed-off-by: Pat Ruddy <pat@voltanet.io>