Add new L3 RPC topic support to Ryu plugin

fixes bug #1224796

This patch adds RPC consumer for the new topic for L3 callbacks to
Ryu plugin.

Change-Id: Id9b3af474e65ab4c5b58121e1dcb160f80a71633
Use same hostname function as nova

Certain plugin implementations of port binding depend on the port's
binding:host_id set by nova matching the compute node's hostname
reported by neutron agents in agents_db. Nova uses
socket.gethostname() to obtain the hostname, so this changes neutron
to also use socket.gethostname(), instead of socket.getfqdn() to
obtain the default hostname. If deployments require a specific
hostname format or value, the hostname can be specified in nova and
neutron configuration files.

Closes-Bug: 1223000
Change-Id: I5de9c6b0df16eca482037a5bdc3a77dc52f4adba
Imported Translations from Transifex

Change-Id: I29024cf2b1f8bf04e7fd57066142665add77eef4
Merge "Use same hostname function as nova"
Merge "Add new L3 RPC topic support to Ryu plugin"