https://github.com/openshift/openshift-ansible/pull/6757

Verified with version openshift-ansible-3.9.0-0.22.0.git.0.0e9d896.el7, there are recommended version of OVS for OCP 3.9.

# vim /usr/share/ansible/openshift-ansible/roles/openshift_health_checker/openshift_checks/ovs_version.py
...
    openshift_to_ovs_version = {
        (3, 4): "2.4",
        (3, 5): ["2.6", "2.7"],
        (3, 6): ["2.6", "2.7", "2.8"],
        (3, 7): ["2.6", "2.7", "2.8"],
        (3, 8): ["2.6", "2.7", "2.8"],
        (3, 9): ["2.6", "2.7", "2.8"],
    }
...

# vim /usr/share/ansible/openshift-ansible/roles/openshift_health_checker/openshift_checks/package_version.py
...
    openshift_to_ovs_version = {
        (3, 4): "2.4",
        (3, 5): ["2.6", "2.7"],
        (3, 6): ["2.6", "2.7", "2.8"],
        (3, 7): ["2.6", "2.7", "2.8"],
        (3, 8): ["2.6", "2.7", "2.8"],
        (3, 9): ["2.6", "2.7", "2.8"],
    }
...

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:0489