ansible: jenkins-slave: enable ntpd

Enable ntpd to prevent clock difference issues reported by jenkins. I
just saw them appearing with one of the new raspberry pis.

Related: https://jenkins.osmocom.org/jenkins/computer/ (shows clock diff)
Change-Id: I2685e60221b0f3baa3f9e6076c01acf37cd38444

ansible/roles/ntpd/README.md

@@ -0,0 +1 @@
+# Install ntpd for debian

ansible/roles/ntpd/tasks/main.yml

@@ -0,0 +1,10 @@
+---
+- name: install ntp from debian
+  apt:
+    name: ntp
+
+- name: start and enable ntp daemon
+  systemd:
+    name: ntp
+    state: started
+    enabled: yes

ansible/setup-jenkins-slave.yml

@@ -42,6 +42,8 @@
       tags:
         - jenkins-slave
 
+    - name: ntpd
+
 - name: setup coverity slaves
   hosts: coverity-slaves
   user: root