We must not only consider files in the current directory (ADF.USIM)
but also in its sub-directories. This requires us to be able to
determine the path we need to traverse between the currently selected
file (EF.UST) and the respective file in some other directory,
which is implemented via CardFile.build_select_path_to().
Change-Id: I61797fefa9dafa36a8a62c11aa2cfaeecb015740