Add stubs for new ovsdbapp API functions
Add stubs for new ovsdbapp API functions

Neutron doesn't use these methods, but they will be added to
ovsdbapp 1.0, and being abstractmethods, would cause an error. The
methods are added in I664add660ce0ec3b0da23325ad38580d850e1f29 and
I9352ffe0f245c579fd766ecd00e8ca512f806798.

Change-Id: Ibfdea4890f7d01ddd38872db40a9829d6b6bdf90

huntxu/neutron,mahak/neutron,eayunstack/neutron,openstack/neutron,mahak/neutron,noironetworks/neutron,noironetworks/neutron,eayunstack/neutron,openstack/neutron,huntxu/neutron,openstack/neutron,mahak/neutron