Set the bridge MAC address to be the same as eth2

On nested environment, when packstack finish to run, the bridge
MAC address is suppose to be the same as the interface otherwise
there is no network flowing (need to investigate this further)

* move sudo from the role to the playbook.

Change-Id: I1ca8ce6dda25a6ec8a9c4fddeb4b8bab9e887a94