If you like your martial arts movies fast, violent and brutal, then “Mayhem!” is for you. The new film from French filmmaker Xavier Gens (“Gangs of London”) stars Nassim Lyes (“Cardo,” “Overdose”) as Sam, a recently-paroled inmate trying to walk the straight line outside prison walls. However, an encounter with his former underworld friends turns violent, forcing Sam and his family to leave France for a peaceful life in Thailand.