Fix build with gcc48: free_func is never NULL.
always initialize the `ret' variable in file() and meta_dirrm() in order to avoid returning undefined value.

The `ret' variable was not initialized, leading to a codepath that could
return garbage value in meta_dirrm(). Also, the file() function was
returning EPKG_OK regardless of the `ret' variable.
Remove the unused `force' variable in exec_fetch().