Duracloud: Handle hidden files in folders

refs #7549

When trying to fetch the contents of a folder, Archivematica passes
'path/to/folder/.' If the folder had files starting with ., they would
be returned when querying with the path as prefix. Only if no files
were returned was the path normalized. This meant non-hidden files were
not fetched if the directory had hidden files in it.

If we think this is a folder, always strip /. and /* from the end of a
path, if they exist.  This removes support for using .. and other
shell-isms from folder paths, but we probably shouldn't be using those
anyway.