Remove default time sources from customisable configuration

It seems unlikely that anyone would want to extend the time servers
variable, so let's keep it simple and not add an additional variable
where one isn't necessary. This is also consistent with how we configure
DNS.

These variables haven't made it into an official release yet, so now
is the time to clean up.

Change-Id: I3c15c6976296abf9c78f1480c1779b854145c7ca

ansible/group_vars/all/time

@@ -10,15 +10,6 @@ timezone: "{{ ansible_date_time.tz }}"
 ###############################################################################
 # Network Time Protocol (NTP).
 
-# Kayobe default time sources
-chrony_ntp_servers_default:
-  - server: pool.ntp.org
-    type: pool
-    options:
-      - option: iburst
-      - option: minpoll
-        val: 8
-
 # List of NTP time sources to configure. Format is a list of dictionaries with
 # the following keys:
 # server:  host or pool
@@ -37,5 +28,10 @@ chrony_ntp_servers_default:
 #       - option: maxsources
 #         val: 3
 #
-chrony_ntp_servers: "{{ chrony_ntp_servers_default }}"
-###############################################################################
+chrony_ntp_servers:
+  - server: pool.ntp.org
+    type: pool
+    options:
+      - option: iburst
+      - option: minpoll
+        val: 8

etc/kayobe/time.yml

@@ -10,9 +10,6 @@
 ###############################################################################
 # Network Time Protocol (NTP).
 
-# Kayobe default time sources
-#chrony_ntp_servers_default:
-
 # List of NTP time sources to configure. Format is a list of dictionaries with
 # the following keys:
 # server:  host or pool