Add pkg/fall for Fallthrough (#1355)

* Add pkg/fall for Fallthrough

Move this into it's own package to facilitate tests. Important bug
was fixed: make the names fully qualified.

Add fall package to hosts, reverse, etcd, and fix kubernetes and any
tests. The k8s tests are still as-is, might need a future cleanup.

plugin/etcd/multi_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/coredns/coredns/plugin/etcd/msg"
 	"github.com/coredns/coredns/plugin/pkg/dnstest"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/plugin/test"
 
 	"github.com/miekg/dns"
@@ -15,7 +16,7 @@ import (
 func TestMultiLookup(t *testing.T) {
 	etc := newEtcdPlugin()
 	etc.Zones = []string{"skydns.test.", "miek.nl."}
-	etc.Fallthrough = true
+	etc.Fall = fall.New()
 	etc.Next = test.ErrorHandler()
 
 	for _, serv := range servicesMulti {