Revert "Cygwin: fstat_helper: always use handle in call to get_file_attribute"

Revert "Cygwin: fstat_helper: always use handle in call to get_file_attribute"

This reverts commit 76dca77f049271e2529c25de8a396e65dbce615d.  That
commit was based on the incorrect assumption that get_stat_handle,
when called on a FIFO in fstat_helper, would always return a handle
that is safe to use for getting the file information.

That assumption is true in many cases but not all.  For example, if
the call to fstat_helper arises from a call to fstat(2) on a FIFO that
has been opened for writing, then get_stat_handle will return a pipe
handle instead of a file handle.