If the file already existed, the WriteResponse.Size was being set
as the length of the entire file, not just the amount that was
written to the existing file.
Fixes#15216
The code looked for /usr/bin/diskutil on darwin, but it's actually
located in /usr/sbin. Fix that by not specifying the absolute path.
Also remove weird timeout construction and extra whitespace.
- Moved fuse related code in a new package, swarm/fuse
- Added write support
- Create new files
- Delete existing files
- Append to files (with limitations)
- More test coverage