NSFS | Versioning | GPFS Linkat & Unlinkat fd verification

[romayalon]

Signed-off-by: Romy romy2232@gmail.com

Explain the changes

2. Fs_napi.unlinkfileat() that calls GPFS unlinkfileat.
3. Fs_napi.getfd() an accessor for fd files.
4. Fs_napi.linkfileat() - added replace_fd and passed it to linkat() for fd verification.
5. GPFS.h - Added the new declarations for linkat & unlinkat
6. namespace_fs - Added safe_move() function that calls safe_move_posix() or safe_move_gpfs() according to the result of _is_gpfs() functions.
7. Namespace_fs.safe_move_gpfs() -
   7.1. Wraps linkfileat() & unlinkfileat() (if requested) calls with retries
   7.2. open dir and file itself in order to unlink it and pass the needed fd
8. Namespace_fs.delete_object() -
   8.1. delete version id & latest - called unlinkfileat with retries.
9. Namespace_fs.delete_multiple_objects() -
   9.1. delete version id & latest - called unlinkfileat with retries.

Issues: Fixed #xxx / Gap #xxx

1. optimization - delete version id - GPFS link overrides, no need to unlink before promoting, but if there is nothing to promote we should
2. move_to_dest retries - checkaccess() when called from upload_object() will fail on temp file since it doesn't exist

Testing Instructions:

• Doc added/updated
• Tests added