nfs41: add a helper to mark layout for return

It marks all matching layout segments as NFS_LSEG_LAYOUTRETURN,
which is an indicator for pnfs_put_lseg() to send layoutreturn,
and also prevents pnfs_update_layout() from using the returning
segments. Once it is set, it never gets cleared.

It also sets proper io failure bit so that pnfs path can be retried
after PNFS_LAYOUTGET_RETRY_TIMEOUT second.

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

diff --cc fs/nfs/pnfs.c
Simple merge

diff --cc fs/nfs/pnfs.h
Simple merge