The booing Red Sox manager John Farrell heard Monday in Dunedin, spring training home of the Blue Jays, is only a foretaste of what he can expect to hear in April, when the Sox go to Toronto for the first weekend of the season. Farrell managed the Jays for two years, a tenure that some in Toronto have likened to an apprenticeship for the job in Boston. Farrell took the Sox job last winter after the Jays agreed to release him from the last year of his contract, and the Sox sent infielder Mike Aviles as compensation (then subsequently shipped Aviles to Cleveland). Red Sox bench coach Torey Lovullo was with Farrell as first base coach in his two years in Toronto. With Farrell in Dunedin, Lovullo managed the Sox split squad playing here. “I’m sure there are going to be some mixed emotions on both sides,’’ Lovullo said of Farrell’s return to Dunedin. “John will go out there, handle it well, and take care of what he needs to take care of.’’