roles/common: Use chrony for NTP on Alpine

roles/common/tasks/ntp.yml

@@ -1,6 +1,7 @@
 ---
 # Hosts running Ubuntu 16.04+ and Debian 9+ use systemd init system and should
 # use timedatectl as a network time client instead of the standalone ntp client.
+# Alpine can use chrony.
 
 - name: Set timezone
   when: timezone is defined and ansible_service_mgr == 'systemd'
@@ -15,4 +16,8 @@
   apt: name=ntp state=absent update_cache=yes
   when: ansible_service_mgr == 'systemd'
 
+- name: Install chronyd on Alpine
+  apt: name=chrony state=present
+  when: ansible_distribution == 'Alpine'
+
 # vim: set ts=2 sw=2: