Always check for namespace collisions on table commands
`-t table -T add|replace ...' would only check for duplicate tables in case
addresses where actually to the table.
Instead of using a positive number of added addresses as prove for
successful table operations, rely on the fact that CREATE_TABLE() is
guaranteed to be called only if pf(4) can be accessed, that is
warn_duplicate_tables() will return.
This improves duplicate detection rate as warnings are now also emitted
even when table commands eventually leave tables unchanged.
OK benno sashan
UnifiedSplitRaw