reverse zone: fix Normalize (#4621)

Make normalize return multiple "hosts" (= reverse zones) when a
non-octet boundary cidr is given.

Added pkg/cidr package that holds the cidr calculation routines; felt
they didn't really fit dnsutil.

This change means the IPNet return parameter isn't needed, the hosts are
all correct. The tests that tests this is also removed: TestSplitHostPortReverse
The fallout was that zoneAddr _also_ doesn't need the IPNet member, that
in turn make it visible that zoneAddr in address.go duplicated a bunch
of stuff from register.go; removed/refactored that too.

Created a plugin.OriginsFromArgsOrServerBlock to help plugins do the
right things, by consuming ZONE arguments; this now expands reverse
zones correctly. This is mostly mechanical.

Remove the reverse test in plugin/kubernetes which is a copy-paste from
a core test (which has since been fixed).

Remove MustNormalize as it has no plugin users.

This change is not backwards compatible to plugins that have a ZONE
argument that they parse in the setup util.

All in-tree plugins have been updated.

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/template/setup.go

@@ -49,16 +49,8 @@ func templateParse(c *caddy.Controller) (handler Handler, err error) {
 			return handler, c.Errf("invalid RR class %s", c.Val())
 		}
 
-		zones := c.RemainingArgs()
-		if len(zones) == 0 {
-			zones = make([]string, len(c.ServerBlockKeys))
-			copy(zones, c.ServerBlockKeys)
-		}
-		for i, str := range zones {
-			zones[i] = plugin.Host(str).Normalize()
-		}
+		zones := plugin.OriginsFromArgsOrServerBlock(c.RemainingArgs(), c.ServerBlockKeys)
 		handler.Zones = append(handler.Zones, zones...)
-
 		t := template{qclass: class, qtype: qtype, zones: zones}
 
 		t.regex = make([]*regexp.Regexp, 0)