Run freebsd-update on `name` poudriere jail

    CLI Example:

    .. code-block:: bash

        salt '*' poudriere.update_jail freebsd:10:x86:64

def update_jail(name):
    '''
    Run freebsd-update on `name` poudriere jail

    CLI Example:

    .. code-block:: bash

        salt '*' poudriere.update_jail freebsd:10:x86:64
    '''
    if is_jail(name):
        cmd = 'poudriere jail -u -j {0}'.format(name)
        ret = __salt__['cmd.run'](cmd)
        return ret
    else:
        return 'Could not find jail {0}'.format(name)