Update RefStack list to 2018.11

Update RefStack list to 2018.11

It sets max_microversion to latest because if both values are not
specified, Tempest avoids tests which require a microversion [1].
Then test_keypairsv22_create_list_show_with_type is skipped and
refstack_defcore fails [2].

It also partially reverts "Allow building containers when
refstack.openstack.org is down" [3].

[1] https://docs.openstack.org/tempest/latest/sampleconf.html
[2] http://artifacts.opnfv.org/functest/functest-opnfv-functest-smoke-latest-refstack_defcore-run-147/results/refstack_defcore/tempest-report.html
[3] https://gerrit.opnfv.org/gerrit/#/c/67232/

Change-Id: Ia87543bb476d3047684e71ddfd05c2aa3f10bbfe
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>