Use Data.Foldable.forM_ instead of hand-rolling whenM

forM_ maps a function over a Foldable from left to right and strings the results
together in a monad.  In this case, the Foldable is (Maybe a) and the result is
the function applied to x for (Just x) and a no-op for Nothing.
Drop r173_14, L9622, and L7160 from the supported legacy branches list

See http://nvidia.custhelp.com/app/answers/detail/a_id/3142 for the legacy
branch support timeline.

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>