At once reassuringly familiar — even starchy — and yet oddly unsatisfying, “The Hitman’s Bodyguard” is meat-and-potatoes moviemaking at its most fungible. Co-starring Ryan Reynolds as Michael Bryce, a disgraced security expert seeking redemption, and Samuel L. Jackson as his nemesis-turned-client Darius Kincaid — a murderer-for-hire Michael must reluctantly protect while Darius prepares to testify against a Belarusian dictator accused of war crimes (Gary Oldman) — the comic action/buddy flick serves up an undistinguished bill of fare. For plot, there’s a bloody yet hard-to-swallow cut of subprime red meat: “The Hitman’s Bodyguard” is gratuitously violent and preposterous.