New Bedford Police say they have their man.  The suspect in yesterday morning's Bank 5 robbery has been arrested...48 year old  Steven Gruenberg of 14 Brook Street in Carver.  Gruenberg was picked up last night at the Rosewood Motel on Cranberry Highway in Wareham.  He had just checked into the motel and was found with heroin and some of the money that was stolen from Bank 5 on Acushnet Ave, New Bedford.   He is scheduled to be arraigned this morning in New Bedford District Court.