Add new tests to presubmit, fix errors

ct/go/util/util_test.go

Index: ct/go/util/util_test.go
diff --git a/ct/go/util/util_test.go b/ct/go/util/util_test.go
index ea0b069f46d413dbfd5590f11cde2d7d9be2651c..efa894097a5d8825ad8e3ae6e1089131d8f4357a 100644
--- a/ct/go/util/util_test.go
+++ b/ct/go/util/util_test.go
@@ -55,7 +55,7 @@ func TestCreateTimestampFile(t *testing.T) {
 	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 {
@@ -67,7 +67,7 @@ func TestCreateTimestampFile(t *testing.T) {
 		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.