nfsd4: make is_open_owner boolean

struct nfs4_stateowner {

	struct list_head        so_strhash;   /* hash by op_name */

	struct list_head        so_stateids;

	int			so_is_open_owner; /* 1=openowner,0=lockowner */

	struct nfs4_client *    so_client;

	/* after increment in ENCODE_SEQID_OP_TAIL, represents the next

	 * sequence id expected from the client: */

	u32                     so_seqid;

	struct xdr_netobj       so_owner;     /* open owner name */

	struct nfs4_replay	so_replay;

	bool			so_is_open_owner;

};

struct nfs4_openowner {