LOS ANGELES (Reuters) – Pop singer Christina Aguilera is in discussions to return as a judge on NBC television singing competition "The Voice" next season, sources with knowledge of the talks said on Tuesday. Aguilera, 32, went on hiatus from the program this season to promote her latest album, "Lotus," with a concert tour. The singer had been a judge on the first three seasons of the program, which debuted in 2011. …