NFSv42: Copy offload should update the file size when appropriate

If the result of a copy offload or clone operation is to grow the
destination file size, then we should update it. The reason is that when
a client holds a delegation, it is authoritative for the file size.

Fixes: 16abd2a0

 ("NFSv4.2: fix client's attribute cache management for copy_file_range")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>