Add new tests to presubmit, fix errors

ct/go/util/util_test.go

 package util
 
 import (
         "fmt"
         "io/ioutil"
         "os"
         "path/filepath"
         "strconv"
         "testing"
 )
@@ skipping 37 matching lines @@
                 t.Error("Unexpected lack of error")
         }
 }
 
 func TestCreateTimestampFile(t *testing.T) {
         realDir := filepath.Join(os.TempDir(), "util_test")
         os.Mkdir(realDir, 0755)
         defer os.RemoveAll(realDir)
         timestampFilePath := filepath.Join(realDir, TIMESTAMP_FILE_NAME)
         if err := CreateTimestampFile(realDir); err != nil {
-                t.Error("Unexpected error: %s", err)
+                t.Errorf("Unexpected error: %s", err)
         }
         // Assert timestamp file exists.
         if _, err := os.Stat(timestampFilePath); err != nil {
                 t.Errorf("Timestamp file %s was not created!", timestampFilePath)
         }
         // Assert timestamp file contains int64.
         fileContent, err := ioutil.ReadFile(timestampFilePath)
         if err != nil {
                 t.Errorf("Unexpected error: %s", err)
         }
         if _, err := strconv.ParseInt(string(fileContent), 10, 64); err != nil {
-                t.Error("Unexpected value in %s: %s", timestampFilePath, err)
+                t.Errorf("Unexpected value in %s: %s", timestampFilePath, err)
         }
 
         // Assert error returned when specified dir does not exist.
         nonexistantDir := filepath.Join(os.TempDir(), "util_test_nonexistant")
         os.RemoveAll(nonexistantDir)
         if err := CreateTimestampFile(nonexistantDir); err != nil {
                 // Expected error
         } else {
                 t.Error("Unexpected lack of error")
         }
 }