When using `ovn_dhcp4_global_options` under `[ovn]` in `ml2_conf.ini` it will cause `neutron server` to crash when attempting to parse the configuration if a key provided contains a list seperated by commas.

For example if setting `domain_search_list` with more than one domain.

[ovn]
ovn_dhcp4_global_options = domain_search_list:foo.bar,baz.qux

Expected output would be that `neutron server` doesn't crash when attempting to parse such configuration and correctly applies these options within `OVN`.

Experienced within OpenStack Epoxy.

Not currently blocking anything as it is possible to patch `_get_ovn_dhcpv4_opts` in `neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py` with the following

options['domain_search_list'] = "\"foo.bar,baz.qux\""

Launchpad bug: https://bugs.launchpad.net/neutron/+bug/2126923