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/cache/setup.go

@@ -41,10 +41,7 @@ func cacheParse(c *caddy.Controller) (*Cache, error) {
 		j++
 
 		// cache [ttl] [zones..]
-		origins := make([]string, len(c.ServerBlockKeys))
-		copy(origins, c.ServerBlockKeys)
 		args := c.RemainingArgs()
-
 		if len(args) > 0 {
 			// first args may be just a number, then it is the ttl, if not it is a zone
 			ttl, err := strconv.Atoi(args[0])
@@ -57,10 +54,8 @@ func cacheParse(c *caddy.Controller) (*Cache, error) {
 				ca.nttl = time.Duration(ttl) * time.Second
 				args = args[1:]
 			}
-			if len(args) > 0 {
-				copy(origins, args)
-			}
 		}
+		origins := plugin.OriginsFromArgsOrServerBlock(args, c.ServerBlockKeys)
 
 		// Refinements? In an extra block.
 		for c.NextBlock() {
@@ -189,11 +184,7 @@ func cacheParse(c *caddy.Controller) (*Cache, error) {
 			}
 		}
 
-		for i := range origins {
-			origins[i] = plugin.Host(origins[i]).Normalize()
-		}
 		ca.Zones = origins
-
 		ca.pcache = cache.New(ca.pcap)
 		ca.ncache = cache.New(ca.ncap)
 	}