There are some usages outside of SpamBlacklist that must be fixed. After
doing that, the signature should be updated to make the user
non-optional.
Note: I've changed the signature because external callers only pass the
first two parameters. Hence, it's easier to change it now, add a
User parameter to the callers and then make it non-optional, than having
to pass $preserveLog and $mode in all callers and then swapping the
order (as that would break the world).
Change-Id: I0714eb9dbc6af3c775ab7a81cb4b59e687183f77
