Description of problem:
OSP11 -> OSP12 upgrade: unable to re-run the upgrade-non-controller.sh script to upgrade a compute node after a failed attempt because the pre-upgrade validations are failing.

Version-Release number of selected component (if applicable):
openstack-tripleo-heat-templates-7.0.3-16.el7ost.noarch
openstack-tripleo-common-7.6.3-6.el7ost.noarch

How reproducible:
100%

Steps to Reproduce:
1. Deploy OSP11
2. Upgrade to OSP12
3. Complete major-upgrade-composable-steps-docker.yaml step successfuly
4. Run upgrade-non-controller.sh --upgrade compute-0 which fails due to unreacheable repositories:

TASK [Upgrade os-net-config] ******************************************************************************************************************************************************************************************************************
fatal: [192.168.24.11]: FAILED! => {"changed": true, "failed": true, "msg": "http://rhos-qe-mirror-brq.usersys.redhat.com/rcm-guest/puddles/OpenStack/12.0-RHEL-7/latest/RH7-RHOS-12.0/x86_64/os/Packages/python2-pbr-3.1.1-1.el7ost.noarch.rpm: [Errno -1] Package does not match intended download. Suggestion: run yum --enablerepo=rhelosp-12.0-puddle clean metadata\nTrying other mirror.\nhttp://rhos-qe-mirror-brq.usersys.redhat.com/rcm-guest/puddles/OpenStack/12.0-RHEL-7/latest/RH7-RHOS-12.0/x86_64/os/Packages/os-net-config-7.3.1-1.el7ost.noarch.rpm: [Errno -1] Package does not match intended download. Suggestion: run yum --enablerepo=rhelosp-12.0-puddle clean metadata\nTrying other mirror.\n\n\nError downloading packages:\n  os-net-config-7.3.1-1.el7ost.noarch: [Errno 256] No more mirrors to try.\n  python2-pbr-3.1.1-1.el7ost.noarch: [Errno 256] No more mirrors to try.\n\n", "rc": 1, "results": ["Loaded plugins: product-id, search-disabled-repos, subscription-manager\nThis system is not registered with an entitlement server. You can use subscription-manager to register.\nResolving Dependencies\n--> Running transaction check\n---> Package os-net-config.noarch 0:6.1.0-2.el7ost will be updated\n---> Package os-net-config.noarch 0:7.3.1-1.el7ost will be an update\n--> Processing Dependency: python-pbr >= 2.0.0 for package: os-net-config-7.3.1-1.el7ost.noarch\n--> Running transaction check\n---> Package python-pbr.noarch 0:1.10.0-2.el7ost will be obsoleted\n---> Package python2-pbr.noarch 0:3.1.1-1.el7ost will be obsoleting\n--> Finished Dependency Resolution\n\nDependencies Resolved\n\n================================================================================\n Package           Arch       Version             Repository               Size\n================================================================================\nInstalling:\n python2-pbr       noarch     3.1.1-1.el7ost      rhelosp-12.0-puddle     191 k\n     replacing  python-pbr.noarch 1.10.0-2.el7ost\nUpdating:\n os-net-config     noarch     7.3.1-1.el7ost      rhelosp-12.0-puddle     260 k\n\nTransaction Summary\n================================================================================\nInstall  1 Package\nUpgrade  1 Package\n\nTotal download size: 451 k\nDownloading packages:\nDelta RPMs disabled because /usr/bin/applydeltarpm not installed.\n"]}

5. Fix repositories issue

6. Re-run upgrade-non-controller.sh --upgrade compute-0

Actual results:
The command fails the pre-upgrade validation check for the neutron-openvswitch-agent service:

TASK [PreUpgrade step0,validation: Check service neutron-openvswitch-agent is running] ********************************************************************************************************************************************************
fatal: [192.168.24.11]: FAILED! => {"changed": true, "cmd": "/usr/bin/systemctl show 'neutron-openvswitch-agent' --property ActiveState | grep '\\bactive\\b'", "delta": "0:00:00.008534", "end": "2017-11-29 12:26:33.244232", "failed": true, "msg": "non-zero return code", "rc": 1, "start": "2017-11-29 12:26:33.235698", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}


Expected results:
We should have a way to disable to pre-upgrade validation checks for the upgrade-non-controller script to allow re-running it after a failed attempt.

Additional info:

Workaround: ssh to the compute node and manually start the services which were stopped during the failed upgrade attempt:

systemctl start neutron-openvswitch-agent

Then re-run the upgrade-non-controller.sh script.