Revert "Use OpenStack Wallaby release"

This reverts commit 3f76d7d1.

The version of IPA images has been pinned to wallaby to ensure they are
compatible with the Wallaby Ironic in current Kolla master images.
Without this, bare metal tests fail with

    'Not found: Extension with id iscsi not found.'

Ironic removed the iscsi driver in Xena.

Change-Id: Ia4c70965d9f3f099046591bac7f702ee982fef71