Get overlay-gateway name on the switch
               Args:
                   callback (function): A function executed upon completion of the
                    method.

               Returns:
                  Dictionary containing details of VXLAN Overlay Gateway.

               Raises:
                   None

def get_overlay_gateway(self):
        """
               Get overlay-gateway name on the switch
               Args:
                   callback (function): A function executed upon completion of the
                    method.

               Returns:
                  Dictionary containing details of VXLAN Overlay Gateway.

               Raises:
                   None
        """
        urn = "urn:brocade.com:mgmt:brocade-tunnels"
        config = ET.Element("config")
        ET.SubElement(config, "overlay-gateway", xmlns=urn)
        output = self._callback(config, handler='get_config')
        result = {}
        element = ET.fromstring(str(output))
        for overlayGw in element.iter('{%s}overlay-gateway' % urn):
            result['name'] = overlayGw.find('{%s}name' % urn).text
            isactivate = overlayGw.find('{%s}activate' % urn)
            if isactivate is None:
                result['activate'] = False
            else:
                result['activate'] = True

            gwtype = overlayGw.find('{%s}gw-type' % urn)
            if gwtype is None:
                result['gwtype'] = None
            else:
                result['gwtype'] = gwtype.text

            attach = overlayGw.find('{%s}attach' % urn)
            if attach is not None:
                rbridgeId = attach.find('{%s}rbridge-id' % urn)
                if rbridgeId is None:
                    result['attached-rbridgeId'] = None
                else:
                    result['attached-rbridgeId'] = rbridgeId.find('{%s}rb-add' % urn).text
                result['attached-vlan'] = None
                vlans = []
                for vlan in attach.iter('{%s}vlan'%urn):
                    vlans.append(vlan.find('{%s}vid' % urn).text)
                result['attached-vlan'] = vlans

        return result