s3/smbd: use SMB_VFS_OFFLOAD_READ_SEND/RECV
No change in behaviour, this just uses the new SMB_VFS_OFFLOAD_READ_SEND
in the duplicate extents and the resume key ioctls.
In the copy-chunk/resume-key case this means using
SMB_VFS_OFFLOAD_READ_SEND to create the resume-key token that is
returned to the client.
In the duplicate-extents case this ensures we can later call
offload-write, which requires a previous call to offload-read that
associates a token with a file-handle.
Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>