Couldn't add more than one database cartridges to openshift app

1. ASSERT: make sure you're using jboss tool version 2.4.0.Final-v20130114-2102-B98 with eclipse 4.2.0
2. EXEC: Create a new openshift user
3. EXEC: Create an app, like python-2.6 app.
4. EXEC: Add cartridge mysql-5.1 and postgresql-8.4.

Excepted results:
Both DB cartridges can be added to the app successfully as it supported to add both database via rhc client.

Actual results:
Error is shown that only 1 embedded database permitted.