controlclient, ipn: adjust tests for authURL semantic changes

The tests cheat at filling out web forms by directly POSTing to
the target. The target for authURLs has changed slightly, the base
authURL now redirects the user to the login page.

Additionally, the authURL cycle now checks the cookie is set
correctly, so we add cookie jars where necessary to pass the
cookie through.

ipn/e2e_test.go

@@ -10,7 +10,10 @@ import (
 	"bytes"
 	"io/ioutil"
 	"net/http"
+	"net/http/cookiejar"
 	"net/http/httptest"
+	"net/url"
+	"strings"
 	"testing"
 	"time"
 
@@ -177,6 +180,13 @@ func newNode(t *testing.T, prefix string, https *httptest.Server) testNode {
 		t.Logf(prefix+": "+fmt, args...)
 	}
 
+	var err error
+	httpc := https.Client()
+	httpc.Jar, err = cookiejar.New(nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	tun := tuntest.NewChannelTUN()
 	e1, err := wgengine.NewUserspaceEngineAdvanced(logfe, tun.TUN(), wgengine.NewFakeRouter, 0)
 	if err != nil {
@@ -200,10 +210,23 @@ func newNode(t *testing.T, prefix string, https *httptest.Server) testNode {
 		Notify: func(n Notify) {
 			// Automatically visit auth URLs
 			if n.BrowseToURL != nil {
-				t.Logf("\n\n\nURL! %vv\n", *n.BrowseToURL)
-				hc := https.Client()
-				_, err := hc.Get(*n.BrowseToURL)
+				t.Logf("BrowseToURL: %v", *n.BrowseToURL)
+
+				authURL := *n.BrowseToURL
+				i := strings.Index(authURL, "/a/")
+				if i == -1 {
+					panic("bad authURL: " + authURL)
+				}
+				authURL = authURL[:i] + "/login?refresh=true&next_url=" + url.PathEscape(authURL[i:])
+
+				form := url.Values{"user": []string{c.LoginName}}
+				req, err := http.NewRequest("POST", authURL, strings.NewReader(form.Encode()))
 				if err != nil {
+					t.Fatal(err)
+				}
+				req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
+
+				if _, err := httpc.Do(req); err != nil {
 					t.Logf("BrowseToURL: %v\n", err)
 				}
 			}