Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/etcd/multi_test.go

@@ -0,0 +1,59 @@
+// +build etcd
+
+package etcd
+
+import (
+	"testing"
+
+	"github.com/coredns/coredns/plugin/etcd/msg"
+	"github.com/coredns/coredns/plugin/pkg/dnsrecorder"
+	"github.com/coredns/coredns/plugin/test"
+
+	"github.com/miekg/dns"
+)
+
+func TestMultiLookup(t *testing.T) {
+	etc := newEtcdMiddleware()
+	etc.Zones = []string{"skydns.test.", "miek.nl."}
+	etc.Fallthrough = true
+	etc.Next = test.ErrorHandler()
+
+	for _, serv := range servicesMulti {
+		set(t, etc, serv.Key, 0, serv)
+		defer delete(t, etc, serv.Key)
+	}
+	for _, tc := range dnsTestCasesMulti {
+		m := tc.Msg()
+
+		rec := dnsrecorder.New(&test.ResponseWriter{})
+		_, err := etc.ServeDNS(ctxt, rec, m)
+		if err != nil {
+			t.Errorf("expected no error, got %v\n", err)
+			return
+		}
+
+		resp := rec.Msg
+		test.SortAndCheck(t, resp, tc)
+	}
+}
+
+// Note the key is encoded as DNS name, while in "reality" it is a etcd path.
+var servicesMulti = []*msg.Service{
+	{Host: "dev.server1", Port: 8080, Key: "a.server1.dev.region1.skydns.test."},
+	{Host: "dev.server1", Port: 8080, Key: "a.server1.dev.region1.miek.nl."},
+	{Host: "dev.server1", Port: 8080, Key: "a.server1.dev.region1.example.org."},
+}
+
+var dnsTestCasesMulti = []test.Case{
+	{
+		Qname: "a.server1.dev.region1.skydns.test.", Qtype: dns.TypeSRV,
+		Answer: []dns.RR{test.SRV("a.server1.dev.region1.skydns.test. 300 SRV 10 100 8080 dev.server1.")},
+	},
+	{
+		Qname: "a.server1.dev.region1.miek.nl.", Qtype: dns.TypeSRV,
+		Answer: []dns.RR{test.SRV("a.server1.dev.region1.miek.nl. 300 SRV 10 100 8080 dev.server1.")},
+	},
+	{
+		Qname: "a.server1.dev.region1.example.org.", Qtype: dns.TypeSRV, Rcode: dns.RcodeServerFailure,
+	},
+}