Re enable DVR with ml2 ovn by default

DVR was enabled by default in ml2 ovn with [1], but was
unintentionally disabled in [2]. This patch re enables it.

[1] https://review.opendev.org/c/openstack/tripleo-heat-templates/+/593056/
[2] https://review.opendev.org/c/openstack/tripleo-heat-templates/+/789142/

Change-Id: Icbd301464609b48b1f54145050d15fab20f7d6ee

deployment/neutron/neutron-plugin-ml2-ovn.yaml

@@ -150,6 +150,7 @@ outputs:
             neutron::plugins::ml2::ovn::dvr_enabled:
               if:
                 - neutron_dvr_set
+                - {get_param: NeutronEnableDVR}
                 - true
           - if:
               - {get_param: EnableInternalTLS}