fix: follow up fix service account credentials createScopedRequired (#605)

Author: arithmetic1728

oauth2_http/java/com/google/auth/oauth2/ServiceAccountCredentials.java

@@ -564,7 +564,7 @@ public static ServiceAccountCredentials fromStream(
   /** Returns whether the scopes are empty, meaning createScoped must be called before use. */
   @Override
   public boolean createScopedRequired() {
-    return scopes.isEmpty();
+    return scopes.isEmpty() && defaultScopes.isEmpty();
   }
 
   /**

oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountCredentialsTest.java

@@ -488,14 +488,23 @@ public void createScopedRequired_emptyScopes() throws IOException {
   }
 
   @Test
-  public void createScopedRequired_nonEmptyScopes_false() throws IOException {
+  public void createScopedRequired_nonEmptyScopes() throws IOException {
     GoogleCredentials credentials =
         ServiceAccountCredentials.fromPkcs8(
             CLIENT_ID, CLIENT_EMAIL, PRIVATE_KEY_PKCS8, PRIVATE_KEY_ID, SCOPES);
 
     assertFalse(credentials.createScopedRequired());
   }
 
+  @Test
+  public void createScopedRequired_nonEmptyDefaultScopes() throws IOException {
+    GoogleCredentials credentials =
+        ServiceAccountCredentials.fromPkcs8(
+            CLIENT_ID, CLIENT_EMAIL, PRIVATE_KEY_PKCS8, PRIVATE_KEY_ID, null, SCOPES);
+
+    assertFalse(credentials.createScopedRequired());
+  }
+
   @Test
   public void fromJSON_getProjectId() throws IOException {
     MockTokenServerTransportFactory transportFactory = new MockTokenServerTransportFactory();