Floating IPs don't work in Ocata

In Newton a floating IP would create a port with the FIP ID set as the device_id reight at creation time.

Change-Id: Ia4c34c6654a5bfb64fbf06b11b0a29b018c6854f in OpenStack Neutron changed this behavior so that now the port is initially created with a device_id set to 'PENDING' which later on gets updated to the FIP ID once the FIP is created in the DB.

This causes the following exception http://paste.openstack.org/show/601060/, which can be viewed more in detail on http://logs.openstack.org/16/422316/3/experimental/gate-tempest-dsvm-networking-odl-carbon-snapshot-vpnservice-v2driver-nv/55f48c2/logs/screen-karaf.txt.gz

The main things that draw attention are:
2017-03-01 09:57:36,492 | WARN | ool-50-thread-53 | FloatingIPListener | 391 - org.opendaylight.netvirt.natservice-impl - 0.4.0.SNAPSHOT | No MAC address found for floating IP 172.24.5.5
2017-03-01 09:57:36,492 | WARN | ool-50-thread-53 | FloatingIPListener | 391 - org.opendaylight.netvirt.natservice-impl - 0.4.0.SNAPSHOT | No neutron Subnet found for floating IP 172.24.5.5

and:
2017-03-01 09:57:36,499 | ERROR | ool-50-thread-53 | VpnFloatingIpHandler | 391 - org.opendaylight.netvirt.natservice-impl - 0.4.0.SNAPSHOT | Failed to send GARP request for floating ip 172.24.5.5 from interface 172294536882577:veth-pub-int:flat
java.lang.NullPointerException: Supplied value may not be null

Therefore, ODL needs to be fixed to accommodate this change of behavior.