Temporary fix for the problem that pg_stat_activity, inet_client_addr(),

and inet_server_addr() fail if the client connected over a "scoped" IPv6
address.  In this case getnameinfo() will return a string ending with
a poorly-standardized "%something" zone specifier, which these functions
try to feed to network_in(), which won't take it.  So that we don't lose
functionality altogether, suppress the zone specifier before giving the
string to network_in().  Per report from Brian Hirt.

TODO: probably someday the inet type should support scoped IPv6 addresses,
and then this patch should be reverted.

Backpatch to 8.2 ... is it worth going further?