The chunked table address functions (set, add, del, clr_astats) add
each chunk's result to the caller's counter without initialising it.
pfctl reuses nadd for the number of tables created, so a replace that
also creates the table is off by one:
pfctl -t foo -T replace 192.0.2.1
reports "2 addresses added".
Zero the counters first, as pfctl_test_addrs() already does. Remove
the workaround for the add case from pfctl (da64f6e047b5), which is
no longer needed.
Add a regression test.
Fixes: 08ed87a4a276 ("pf: convert DIOCRSETADDRS to netlink")
MFC after: 1 week
Sponsored by: Rubicon Communications, LLC ("Netgate")