propagator: Fix folder duplication if the folder is renamed on the server while uploading

While uploading a new folder, if the folder is renamed on the server
when still uploading, the result will be that the files that are already
uploaded will end up in the new filder name, but the file that were
not still are in the old folder.

After renaming, all the new uploads wil fail with an error on this sync
because the parent directory don't exist.
But they were uploaded with the old name in the next sync because
the renaming was not detected because the file id was not in the DB

Fix the problem by fetching the file id always when creating a new
directory, on the next sync, and saving it in the database ummediatly

https://github.com/owncloud/enterprise/issues/191