More MTU cleanups for Neutron

Since Mitaka, Neutron does the right job, calculating MTU for networks
and advertising them thru DHCP and RA.

1. Don't disable MTU advertisement in neutron.conf (advertise_mtu).
2. Don't disable MTU calculation (path_mtu = 0, segment_mtu = 0).
3. Don't set network_device_mtu (it breaks data path and is deprecated).

Change-Id: I28536c5a13711c8e82d056fb47567234aab4e547

defaults/main.yml

@@ -336,7 +336,6 @@ neutron_agent_mode: legacy
 neutron_agent_down_time: 120
 neutron_agent_polling_interval: 5
 neutron_report_interval: "{{ neutron_agent_down_time | int / 2 | int }}"
-neutron_network_device_mtu: 1450
 
 # L3HA configuration options.
 neutron_ha_vrrp_auth_type: PASS

releasenotes/notes/neutron-mtu-cleanup-ce73693b4f7aef0d.yaml

@@ -0,0 +1,9 @@
+---
+upgrade:
+  - As described in the `Mitaka release notes
+    <http://docs.openstack.org/releasenotes/neutron/mitaka.html>`_
+    Neutron now correctly calculates for and advertises the MTU to
+    instances. As such the ``neutron_network_device_mtu`` variable
+    has been removed and the hard-coded values in the templates for
+    ``advertise_mtu``, ``path_mtu``, and ``segment_mtu`` have been
+    removed to allow upstream defaults to operate as intended.

templates/neutron.conf.j2

@@ -13,7 +13,6 @@ log_file = /var/log/neutron/neutron.log
 {% if inventory_hostname in groups[neutron_services['neutron-server']['group']] %}
 
 # General, only applies to neutron server host group
-network_device_mtu = {{ neutron_network_device_mtu }}
 allow_overlapping_ips = True
 vlan_transparent = False
 
@@ -79,7 +78,6 @@ rpc_workers = {{ neutron_rpc_workers }}
 dhcp_agent_notification = True
 dhcp_agents_per_network = {{ dhcp_agents_max }}
 dhcp_lease_duration = 86400
-advertise_mtu = False
 
 # Nova notifications
 notify_nova_on_port_status_changes = True

templates/plugins/ml2/ml2_conf.ini.j2

@@ -7,9 +7,6 @@ tenant_network_types = {{ neutron_provider_networks.network_types }}
 mechanism_drivers = {{ neutron_plugins[neutron_plugin_type].mechanisms }}
 extension_drivers = port_security{% if 'qos' in neutron_plugin_base %},qos{% endif %}
 
-path_mtu = 0
-segment_mtu = 0
-
 {% if neutron_provider_networks.network_flat_networks is defined %}
 
 # ML2 flat networks