Split upgrade testing into it's own shell script

This will separate out the runs so that variables and modules are not
re-used across runs - ensuring the latest modules and versions are used,
and ensuring multiple versions of the tests playbook aren't required on
non-upgrade runs.

Change-Id: Icaeb360a6302ff207d970c0c6fe8e56add1e1327

tox.ini

@@ -115,14 +115,13 @@ deps =
 setenv =
     {[testenv]setenv}
     TEST_PLAYBOOK={toxinidir}/tests/test-upgrade.yml
-    ANSIBLE_INVENTORY={toxinidir}/tests/upgrades-inventory
 commands =
     {[testenv:tests_clone]commands}
     bash -c "if [ ! -d "{toxinidir}/tests/common/previous" ]; then \
                git clone -b stable/ocata https://git.openstack.org/openstack/openstack-ansible-tests \
                  {toxinidir}/tests/common/previous; \
              fi"
-    bash -c "{toxinidir}/tests/common/test-ansible-functional.sh"
+    bash -c "{toxinidir}/tests/test-nova-upgrades.sh"
 
 
 [testenv:func_lxd]