ntp.j2: add system time zone config

UTC is hardcoded for now.

geant/gap_ansible/roles/base_config/templates/routers/nokia/ntp.j2

   <system>
       <time>
+          <zone alu:operation="replace">
+              <standard>
+                  <name>utc</name>
+              </standard>
+          </zone>
           <ntp alu:operation="replace">
           {% for server in system_ntp.servers %}
               <server xmlns="urn:nokia.com:sros:ns:yang:sr:conf" xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0" xmlns:nokia-attr="urn:nokia.com:sros:ns:yang:sr:attributes">