nfs/filelayout: use pnfs_error_mark_layout_for_return

Instead of calling layoutreturn directly, call pnfs_error_mark_layout_for_return
to mark layouts for return and let generic code return layout when
layout segments are freed.

Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Tom Haynes <Thomas.Haynes@primarydata.com>

Conflicts:
	fs/nfs/filelayout/filelayout.c