add ntp template

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

+  <system>
+      <time>
+          <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">
+                  <ip-address>{{ server.address }}</ip-address>
+                  <router-instance>Base</router-instance>
+                  {% if server.key is defined %}
+                  <key-id>{{server.key}}</key-id>
+                  {% endif %}
+              </server>
+          {% endfor %}
+          {% for key in system_ntp.ntp_keys %}
+              <authentication-key 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">
+                  <key-id>{{ key.id }}</key-id>
+                  <key>{{ key.nokia_key_hash }}</key>
+                  <type>message-digest</type>
+              </authentication-key>
+          {% endfor %}
+          </ntp>
+      </time>
+  </system>