Ansible: Add a clock sync to OpenWRT hosts in the update playbook.

If the clock drift is too big (I've seen a month) then certificate
validation fails and fetching updates fails.

Ansible/update.yaml

@@ -69,6 +69,11 @@
       tags:
         - openwrt
       block:
+        # Sometimes the clock is not synced, the date is wrong and certificate
+        # validation during downloads fails.
+        - name: Sync clock
+          command: ntpd -n -q -p 0.openwrt.pool.ntp.org -p 1.openwrt.pool.ntp.org -p 2.openwrt.pool.ntp.org -p 3.openwrt.pool.ntp.org
+
         - name: Update package list
           command: opkg update
           changed_when: false