We should never allow either the broadcast or IN_ADDR_ANY to be
connected to or sent to. This was fond when working with Michael
Tuexen and Skyzaller. Skyzaller seems to want to use either of
these two addresses to connect to at times. And it really is
an error to do so, so lets not allow that behavior.

Sponsored by: Netflix Inc.
Differential Revision: https://reviews.freebsd.org/D24852