roles/jenkins-slave: Prepare host for Jenkins

The *jenkins-slave* role prepares a host to have the Jenkins slave
agent deployed on it. Deploying the agent itself is done by the Jenkins
master, through the web UI.

roles/jenkins-slave/tasks/main.yml

@@ -0,0 +1,42 @@
+- name: ensure required packages are installed
+  package:
+    name={{ jenkins_slave_required_packages|join(',') }}
+    state=present
+  tags:
+  - install
+
+- name: ensure jenkins group exists
+  group:
+    name=jenkins
+    system=yes
+- name: ensure jenkins user exists
+  user:
+    name=jenkins
+    system=yes
+    home=/var/lib/jenkins
+    createhome=yes
+    groups=jenkins
+    append=yes
+    state=present
+- name: ensure jenkins home directory permissions are correct
+  file:
+    path=/var/lib/jenkins
+    owner=jenkins
+    group=jenkins
+    mode=0755
+    state=directory
+
+- name: ensure jenkins ssh client directory exists
+  file:
+    path=/var/lib/jenkins/.ssh
+    owner=jenkins
+    group=jenkins
+    mode=0700
+    setype=ssh_home_t
+    state=directory
+- name: ensure jenkins master ssh key is authorized
+  authorized_key:
+    user: jenkins
+    key: '{{ jenkins_master_ssh_key }}'
+    state: present
+  when: jenkins_master_ssh_key is defined

roles/jenkins-slave/vars/main.yml

@@ -0,0 +1,3 @@
+jenkins_slave_required_packages:
+- git-core
+- java-1.8.0-openjdk-headless