“The Music Man” swung into high gear last Thursday thanks to one “swing actor.”Two-time Tony Award winner Hugh Jackman took a few moments out of Thursday’s preview to thank his co-star for the evening, and got a little “emotional” while doing so.Jackman, 53, plays charming con artist Harold Hill in Meredith Wilson’s ragtime musical, opposite Sutton Foster, 46, as do-gooder piano teacher Marian.But when Foster, 46, became suddenly unavailable for the show’s fourth preview, understudy Kathy