NFS41: remove NFS_LAYOUT_ROC flag

If we return delegation before closing, we fail to do roc check
during close because NFS_LAYOUT_ROC is cleared by delegreturn
and it causes layouts to be still hanging around after delegreturn
+ close, which is a voilation against protocol.

Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>