mw/logs: add rflags to logging (#845)

Add the DNS message response flags as {rflags} to the default logging
Also complete the replacer testing that is was commented out.
And (unrelated) Switch erratic and whoami to ease testing.

Note: {flags} could and should be added as well - but we can leave that
as a beginners bug.

core/dnsserver/zdirectives.go

@@ -35,8 +35,8 @@ var directives = []string{
 	"secondary",
 	"etcd",
 	"proxy",
-	"whoami",
 	"erratic",
+	"whoami",
 	"startup",
 	"shutdown",
 }