By Hugh Bronstein BUENOS AIRES (Reuters) – Argentine leader Cristina Fernandez's allies took a beating in Sunday's midterm election, shrinking her congressional majority, snuffing out chances of a constitutional change to allow her a third term and kicking off the contest to succeed her in 2015. Voters chose half of the lower house of Congress and a third of the Senate in Sunday's midterm. Re-elected in 2011 on promises of increasing state control in Latin America's No. …