Correct the behavior of the utils_expand_path function

Even if the utils_expand_path function was intended to allow to
use unexistent directory paths, it was in fact only working for
some kind of arguments. Paths like "foo", "bar/" or "bar/foo"
when the "bar" directory does not exist wasn't working. This
patch introduce a new way to expand paths in this function that
also works properly for these kind of arguments.

Signed-off-by: Raphaël Beamonte <raphael.beamonte@gmail.com>