NEW YORK -(Dow Jones)- Private businesses added a modest number of jobs in August, according to a report released Wednesday. Private-sector jobs in the U.S. rose by 91,000 this month, ... had expected ADP would report an August gain of 100,000. The July data were revised down to show a rise of 109,000 versus 114,000 reported earlier. ...Economists surveyed by Dow Jones Newswires expect total nonfarm payrolls rose by only 80,000 slots in August. This month's number is expected to be held down by workers on strike at Verizon Communications Inc. (VZ) in mid-August and layoffs in the state and...