Read response from http.Get() in TestWebInterface, so http.Get() does…

… not hang (google#315)

* fix TestWebInterface

* check errors in modified portion of TestWebInterface

* use defer wg.Done()

internal/driver/webui_test.go

@@ -119,8 +119,15 @@ func TestWebInterface(t *testing.T) {
 		for count := 0; count < 2; count++ {
 			wg.Add(1)
 			go func() {
-				http.Get(path)
-				wg.Done()
+				defer wg.Done()
+				res, err := http.Get(path)
+				if err != nil {
+					t.Error("could not fetch", c.path, err)
+					return
+				}
+				if _, err = ioutil.ReadAll(res.Body); err != nil {
+					t.Error("could not read response", c.path, err)
+				}
 			}()
 		}
 	}