Revert "Remove adjust-interface-mtus script"

This reverts commit c1d0eb1c87.

Since this was fixed in queens/master, we don't need to run it in queens
and master so we've added a release clause.

Change-Id: I8b5b6ed983b1560f9f834abd8a54ae53b4db3465
Related-Bug: #1760189

roles/baremetal-prep-overcloud/tasks/adjust-mtu-dnsmasq-ironic.yml

@@ -0,0 +1,15 @@
+---
+
+- name: Copy over adjust interface mtus script template
+  template:
+    src: adjust-interface-mtus.sh.j2
+    dest: "{{ working_dir }}/adjust-interface-mtus.sh"
+    mode: 0755
+
+- name: Adjust MTU values and modify dnsmasq-ironic.conf
+  become: yes
+  shell: >
+    "{{ working_dir }}"/adjust-interface-mtus.sh
+  when: step_adjust_mtu|bool
+
+

roles/baremetal-prep-overcloud/tasks/main.yml

@@ -1,4 +1,8 @@
 ---
+# this was fixed in queens/master
+- include: adjust-mtu-dnsmasq-ironic.yml
+  when: release in ['newton', 'ocata', 'pike']
+
 - include: allow-traffic-for-controller.yml
 
 - include: install-upstream-ipxe.yml

roles/baremetal-prep-overcloud/templates/adjust-interface-mtus.sh.j2

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+set -eux
+
+### --start_docs
+
+## Adjust interface MTU valuesfor undercloud and overcloud
+## =======================================================
+
+## * Adjust interface mtus
+## ::
+
+{% for interface in (mtu_interface) %}
+    ip link set {{ interface }} mtu {{ mtu }}
+    echo "MTU={{ mtu }}" >> /etc/sysconfig/network-scripts/ifcfg-{{ interface }}
+{% endfor %}
+
+## * Modify dnsmasq-ironic.conf
+## ::
+
+echo -e "\ndhcp-option-force=26,{{ mtu }}" >> /etc/dnsmasq-ironic.conf
+systemctl restart 'neutron-*'
+systemctl restart openstack-ironic-conductor
+
+### --stop_docs