Add Molecule tests for 'dns' role

This commit supplements 'Molecule test for
infrastructure playbook' with role level tests.

Change-Id: I14cdeedf1c80c0ee06bacf0a391ee1d7ccd6df55
Issue-ID: OOM-1841
Signed-off-by: Bartek Grzybowski <b.grzybowski@partner.samsung.com>
7 files changed