For the second time in as many days, power companies today were forced to shut down electricity to customers statewide as California came the closest it has this season to running out of power, state officials said.As late as tonight, energy officials were concerned that they would be forced to announce a last-resort emergency as power reserves crept close to a dangerous level of 1.5 percent, and utility companies would have been required to institute rolling hourlong blackouts in various parts of the state. Such last-resort steps have never been taken in California before.