“Mechanic: Resurrection” is a dumb movie. A bag of hammers might provoke more intellectual discussion than the latest from German director Dennis Gansel (“The Wave”). But it’s not oblivious. There’s a faint twinkle in its eye. There’s not a lot happening upstairs, but Gansel and screenwriters Philip Shelby and Tony Mosher are at least willing to keep things loose. The plot structure can best be described as flexible. The action is often ludicrous. It has an almost gleeful disregard to believability when jumping between global set pieces and exotic locales. But that’s what makes its rather dull presentation fairly disheartening. It’s sillier and more free-wheeling than you’d initially expect, but it never quite finds a sense of drive to give it purpose.