Comment 0 for bug 1674889

When thread of ovn ovsdb-server is not present, then start or restart neutron-server, manager was set to openvswitch. Neutron-server can no longer connect to ovn ovsdb occupied port 6642 unless delete manager manually.
Manager "ptcp:6642:10.157.0.159"
    Bridge br-int
        fail_mode: secure

This is not a bug that always exists, it's caused by some neutron recent modification.
I submit a bug[1] in neutorn a few days ago, then I get from terry wilson that ovsdb native API in neutron with be replaced by ovsapp in this cycle, so I dropped that patch and will fix this bug in networking-ovn by a simple change, using idlutils._get_schema_helper instead of idlutils.get_schema_helper.

[1] https://bugs.launchpad.net/neutron/+bug/1672590