server: remove if registry != nil code (#2735)

I can't find what's this code should be doing and it looks like it's
not doing anything.
Signed-off-by: Miek Gieben <miek@miek.nl>

core/dnsserver/server.go

@@ -66,22 +66,8 @@ func NewServer(addr string, group []*Config) (*Server, error) {
 		}
 		// set the config per zone
 		s.zones[site.Zone] = site
+
 		// compile custom plugin for everything
-		if site.registry != nil {
-			// this config is already computed with the chain of plugin
-			// set classChaos in accordance with previously registered plugins
-			for name := range EnableChaos {
-				if _, ok := site.registry[name]; ok {
-					s.classChaos = true
-					break
-				}
-			}
-			// set trace handler in accordance with previously registered "trace" plugin
-			if handler, ok := site.registry["trace"]; ok {
-				s.trace = handler.(trace.Trace)
-			}
-			continue
-		}
 		var stack plugin.Handler
 		for i := len(site.Plugin) - 1; i >= 0; i-- {
 			stack = site.Plugin[i](stack)