Yes it is extremely annoying isn't it?
To turn it off you go to Edit Preferences and then Site.
Then in Dependent files take the tick out of Prompt on get and Prompt on put. Apparently this turns off the automatic sync as per this help note in the forum:
Displays a prompt for transferring dependent files (such as images, external style sheets, and other files referenced in the HTML file) that the browser loads when it loads the HTML file. By default, both Prompt on Get/Check Out and Prompt on Put/Check In are selected.
It’s usually a good idea to download dependent files when checking out a new file, but if the latest versions of the dependent files are already on the local disk, there’s no need to download them again. This is also true for uploading and checking in files: no need if up-to-date copies are already at the destination.
If you deselect these options, your dependent files are not transferred. Therefore, to force the Dependent Files dialog box to appear even when these options are deselected, hold down Alt (Windows) or Option (Macintosh) while choosing the Get, Put, Check In, or Check Out commands.
So it is not obvious, but this is how you stop automatic sync every time you change your files in DW CC 2014 or save them.
However be warned, turning this off seems to stop Live View working. I have put a question about this in the forum and am awaiting an answer.