Update refstack test version to 2018.02
Update refstack test version to 2018.02

To conform with Openstack Queens

Change-Id: I7d65a1d7fe7c9a30e2c00a8a0eac2ab3fe1b9428
Signed-off-by: Linda Wang <81613bebe84fa394bbc7c5cc1c21989c9bff2c52@huawei.com>

opnfv/functest,opnfv/functest