FOR a while, it seemed as though audiences might be singing the blues instead of hearing them in Riverhead next weekend. The board of the Vail-Leavitt Music Hall, which has run the Riverhead Blues and Music Festival since 2006, and the Riverhead Chamber of Commerce both sought permits to hold the same festival in the same place at the same time. Local news reports referred to political squabbling, and Newsday reported that perhaps there would be no festival at all.