allow HTTP 201 & 204 when storing remote state

Apache mod_dav returns 201 (created) and 204 (no content) during PUTs;
treat these as valid responses when using Apache as a http backend.

state/remote/http.go

@@ -313,7 +313,7 @@ func (c *HTTPClient) Put(data []byte) error {
 
 	// Handle the error codes
 	switch resp.StatusCode {
-	case http.StatusOK:
+	case http.StatusOK, http.StatusCreated, http.StatusNoContent:
 		return nil
 	default:
 		return fmt.Errorf("HTTP error: %d", resp.StatusCode)

state/remote/http_test.go

@@ -31,6 +31,14 @@ func TestHTTPClient(t *testing.T) {
 	client := &HTTPClient{URL: url, Client: cleanhttp.DefaultClient()}
 	testClient(t, client)
 
+	// test just a single PUT
+	p := &HTTPClient{
+		URL:          url,
+		UpdateMethod: "PUT",
+		Client:       cleanhttp.DefaultClient(),
+	}
+	testClient(t, p)
+
 	// Test locking and alternative UpdateMethod
 	a := &HTTPClient{
 		URL:          url,
@@ -134,12 +142,18 @@ func (h *testHTTPHandler) Handle(w http.ResponseWriter, r *http.Request) {
 	switch r.Method {
 	case "GET":
 		w.Write(h.Data)
-	case "POST", "PUT":
+	case "PUT":
+		buf := new(bytes.Buffer)
+		if _, err := io.Copy(buf, r.Body); err != nil {
+			w.WriteHeader(500)
+		}
+		w.WriteHeader(201)
+		h.Data = buf.Bytes()
+	case "POST":
 		buf := new(bytes.Buffer)
 		if _, err := io.Copy(buf, r.Body); err != nil {
 			w.WriteHeader(500)
 		}
-
 		h.Data = buf.Bytes()
 	case "LOCK":
 		if h.Locked {