DUBAI, United Arab Emirates – The fast-growing Abu Dhabi state investment fund with the biggest stake in the maker of Mercedes-Benz said Thursday it has snapped up nearly 5 percent of UniCredit, Italy's largest bank.Although Aabar Investments didn't say how much it paid, the deal is worth about 1.8 billion euros ($2.2 billion), based on the number of UniCredit shares outstanding at the clos