Directories aren't closed in 'Formulation_Manager::get_forcing_params`

[christophertubbs]

There are two return statements in Formulation_Manager::get_forcing_params that don't call closedir before exiting the function. closedir should probably be called after the forcing object is created and before returning or an RAII object should be created to wrap the directory object to ensure it is always closed when exiting scope.

Failing to address this may result in file handle leaks.

NOTE: I'm obviously not the C++ expert here, so this can probably be closed outright if there's something non-obvious that performs the clean up. If that's the case, though, a nice comment may be helpful.