Change uses of fileExistsAtPath to isUbiquitousItemAtURL

[simonp2014]

If I am understanding this correctly the use of fileExistsAtPath need to be reviewed to see if isUbiquitousItemAtURL should be used instead. I ran into the issue with using deleteDocumentWithName on a document that had not been downloaded

I think there are more operations that would not work correctly if a document had not been downloaded, e.g. rename

[willlarche]

Yeah I'm having this exact problem. Since it doesn't find the file (that's briefly .[file name].cloud) it goes right to create the file. And I get all these duplicates appended with a count in the title.