It’s hard enough wrestling with a dog who hates bath time or a cat who turns your arms into scratching posts when it’s nail-trimming time, whether you do it yourself or corral them into a carrier or crate for a trip to the groomer’s. To keep the fur from flying, more pet owners around the country are turning to mobile grooming services, a growing niche in the seemingly recession-proof category of stuff and services we buy our pets. Mobile groomers use vans or buses that have been overhauled into “salons” for four-footed customers, with tubs, blow-dryers and clipping stations for fur and nails.