nfsd4: handle seqid-mutating open errors from xdr decoding

If a client sets an owner (or group_owner or acl) attribute on open for
create, and the mapping of that owner to an id fails, then we return
BAD_OWNER.  But BAD_OWNER is a seqid-mutating error, so we can't
shortcut the open processing that case: we have to at least look up the
owner so we can find the seqid to bump.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/xdr4.h

@@ -237,6 +237,7 @@ struct nfsd4_open {
 	u32		op_share_deny;      /* request */
 	u32		op_deleg_want;      /* request */
 	stateid_t	op_stateid;         /* response */
+	__be32		op_xdr_error;       /* see nfsd4_open_omfg() */
 	u32		op_recall;          /* recall */
 	struct nfsd4_change_info  op_cinfo; /* response */
 	u32		op_rflags;          /* response */