NFSv4.1 LAYOUTRETURN implementation

Currently, does not support layout-type payload encoding.
Signed-off-by: NAlexandros Batsakis <batsakis@netapp.com>
Signed-off-by: NAndy Adamson <andros@citi.umich.edu>
Signed-off-by: NAndy Adamson <andros@netapp.com>
Signed-off-by: NDean Hildebrand <dhildeb@us.ibm.com>
Signed-off-by: NFred Isaman <iisaman@citi.umich.edu>
Signed-off-by: NFred Isaman <iisaman@netapp.com>
Signed-off-by: NMarc Eshel <eshel@almaden.ibm.com>
Signed-off-by: NZhang Jingwang <zhangjingwang@nrchpc.ac.cn>
[call pnfs_return_layout right before pnfs_destroy_layout]
[remove assert_spin_locked from pnfs_clear_lseg_list]
[remove wait parameter from the layoutreturn path.]
[remove return_type field from nfs4_layoutreturn_args]
[remove range from nfs4_layoutreturn_args]
[no need to send layoutcommit from _pnfs_return_layout]
[don't wait on sync layoutreturn]
[fix layout stateid in layoutreturn args]
[fixed NULL deref in _pnfs_return_layout]
[removed recaim member of nfs4_layoutreturn_args]
Signed-off-by: NBenny Halevy <bhalevy@panasas.com>