sockstat: change check for wildcard sockets to avoid historical classes

sockstat was checking whether a bound address was "host 0", the lowest
host on a network, using inet_lnaof(). This only works for class A/B/C.
However, it isn't useful to bind such an address unless it is really
the unspecified address INADDR_ANY. Change the check to to use that.

MFC after: 1 month
Reviewd by: tuexen
Differential Revision: https://reviews.freebsd.org/D32715