Fix .push python-ibm-db-django polluting common attribute

A Common attribute was having a dashboard specific package added to it.
This has side effects as it will effect other cookbooks using that
attribute.

* Create attrbute to hold dashboard specific database packages
* Tests unchanged as they are still correct outcome

Change-Id: I99768ae91ed0db9f632d2529014130c38096f8fe
Closes-Bug: #1364508