Updates a distributed virtual portgroup

    portgroup_ref
        The portgroup reference

    spec
        Portgroup spec (vim.DVPortgroupConfigSpec)

def update_dvportgroup(portgroup_ref, spec):
    '''
    Updates a distributed virtual portgroup

    portgroup_ref
        The portgroup reference

    spec
        Portgroup spec (vim.DVPortgroupConfigSpec)
    '''
    pg_name = get_managed_object_name(portgroup_ref)
    log.trace('Updating portgrouo %s', pg_name)
    try:
        task = portgroup_ref.ReconfigureDVPortgroup_Task(spec)
    except vim.fault.NoPermission as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareApiError(
            'Not enough permissions. Required privilege: '
            '{0}'.format(exc.privilegeId))
    except vim.fault.VimFault as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareApiError(exc.msg)
    except vmodl.RuntimeFault as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareRuntimeError(exc.msg)
    wait_for_task(task, pg_name, six.text_type(task.__class__))