'Add validation for update_policy.'

def validate(self):

    self.validate_launchconfig()
    super(InstanceGroup, self).validate()
    if (self.update_policy is not None):
        policy_name = self.ROLLING_UPDATE
        if ((policy_name in self.update_policy) and (self.update_policy[policy_name] is not None)):
            pause_time = self.update_policy[policy_name][self.PAUSE_TIME]
            if (iso8601utils.parse_isoduration(pause_time) > 3600):
                msg = (_('Maximum    %s    is    1    hour.') % self.PAUSE_TIME)
                raise ValueError(msg)
