Update Openstack, add missed steps to upgrade computes

Additional changes:
 * Refactored switch_to_proposed_pipelines to avoid multiply executions

Change-Id: If9b0c460bdbf41b8248dc3cb5f0d2f486b47e954
diff --git a/tcp_tests/fixtures/underlay_fixtures.py b/tcp_tests/fixtures/underlay_fixtures.py
index a8856d6..1cfae51 100644
--- a/tcp_tests/fixtures/underlay_fixtures.py
+++ b/tcp_tests/fixtures/underlay_fixtures.py
@@ -158,7 +158,7 @@
     request.addfinalizer(test_fin)
 
 
-@pytest.fixture(scope="function")
+@pytest.fixture(scope="session")
 def underlay_actions(config):
     """Fixture that provides SSH access to underlay objects.