Upgrade netconf_client for tests and create a new docker image

[mattiaswal]

This since they now have added get-data RPC which we have patched on our own. infamy/netconf.py:

 def _get_data(self, xpath,as_xml=False):
        """Local member wrapper for netconf-client  RPC"""
        # pylint: disable=protected-access
        (raw, ele) = self.ncc._send_rpc(self._ncc_get_data_rpc(filter=xpath))
        data = NccGetDataReply(raw, ele)
        if(as_xml):
            return data

From netconf_client:

add support for the  command from RFC 8526