LU-15683 ofd: proper initialize filter_fid in ofd fallocate

LU-15683 ofd: proper initialize filter_fid in ofd fallocate

Intialize filter_fid buffer and call xattr set XATTR_NAME_FID properly
in ofd_object_fallocate().

Lustre-change: https://review.whamcloud.com/46919
Lustre-commit: TBD (from c77a4635286e5b74034bf6ff65db75bc79e10564)

Fixes: 48457868a02 ("LU-3606 fallocate: Implement fallocate preallocate operation")
Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: Ied573c39dde77f935622e9fbedb2d71eb3bd8f5d
Reviewed-on: https://review.whamcloud.com/46924
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>