Create set_hostname role and playbook

Turns out we have had many issues with random servers having
wrong hostname and /etc/hosts info.
This playbook/role allows to configure that by passing
-e "target=<hostname>" as ansible-playbook parameter.

Change-Id: I73939ebc65211a840bb41370c22b111112389716

playbooks/roles/set_hostname/tasks/main.yml

@@ -0,0 +1,13 @@
+---
+# Set hostname and /etc/hosts
+# Inspired by:
+# https://github.com/ansible/ansible/pull/8482)
+# https://gist.github.com/rothgar/8793800
+- name: Set /etc/hostname
+  hostname: name="{{ inventory_hostname.split('.', 1)[0] }}"
+
+- name: Set /etc/hosts
+  template: src=hosts.j2 dest=/etc/hosts mode=0644
+
+- name: Set /etc/mailname
+  template: src=mailname.j2 dest=/etc/mailname mode=0644

playbooks/roles/set_hostname/templates/hosts.j2

@@ -0,0 +1,2 @@
+127.0.0.1 localhost
+127.0.1.1 {{ inventory_hostname }} {{ inventory_hostname.split('.', 1)[0] }}

playbooks/roles/set_hostname/templates/mailname.j2

@@ -0,0 +1 @@
+{{ inventory_hostname.split('.', 1)[0] }}

playbooks/set_hostnames.yml

@@ -0,0 +1,7 @@
+---
+# file: set_hostnames.yml
+- hosts: "{{ target }}"
+  gather_facts: no
+  user: root
+  roles:
+    - { role: set_hostname }