By Nivedita Bhattacharjee CHICAGO (Reuters) - Qatar Airways Chief Executive Officer Akbar Al Baker said he hopes that all five of the airline's Boeing 787s will be back in service by the end of April, as confidence grows in the industry that regulators may be close to declaring the jet safe. Speaking at the launch of Qatar's service to Chicago, Al Baker also said he thinks Boeing's fix for the battery system that overheated on two planes in January will work. He said if it were not the right solution, the Federal Aviation Administration would not have approved the testing plan for it. ...