A Cook County jury on Tuesday awarded $5.3 million to a man who needed a spinal fusion after slipping on snow and ice while wearing an oily boot.Plaintiff Christopher Cravatta, a locomotive engineer for Metra, sued the rail agency in 2014, alleging it allowed him to use an unsafe engine that had oil pooling on its floor, which led, along with the ice and snow, to his slip in December 2013.Cravatta, who was 30 years old at the time, was transferring a train from Metra’s Western Avenue Coach Yard to Union Station at …