reorg: simplifies packstack roles

- moves all answer_file generation to a simple role generate answers
- deletes packstack-neutron-aio, nova-aio, quantum-aio, rhos/epel roles
- multinode role now generates the packstack answer for aio and
  multinode jobs

Change-Id: I6d07788cd68395826efc00fe2fcb119c83c2b9aa
reorg: merge packstack aio and multinode playbook

Change-Id: Ibf65e8ffc00bca22fe37d15267d7e02e4eccff44