Each summer, studios drop a late-season, B-grade thriller into theaters in hopes of seeing it make a run at a dark horse weekend. 2005: Into the Blue and Red Eye. Last year: Death Race and Mirrors. Two of those four qualify for a the Showcase of Shame and both, incidentally, were not released in 2008. But so much for old memories. It’s summer 2009 and this year we’ve got A Perfect Getaway. Written and directed by the very capable craftsman …