The fifth season of Denis Leary’s “Rescue Me” doesn’t premiere for two months, but FX is already ordering a sixth round. The network picked up another 18 episodes of the critically acclaimed show about the lives of New York firefighters. The 22-episode fifth season, which was delayed by last year’s writers strike, starts April 7, about 19 months after the conclusion of Season 4. In addition, Leary is launching “The Rescue Me Comedy Tour,” an 11-city tour featuring the actor, fellow comedians and “Rescue Me” co-stars Adam Ferrara and Lenny Clarke.