Added a field to the SVCXPRT structure that the nfsv4 server can

use to identify if the socket is the same one that a cached request
	came in on. It is set by nfsrvd_addsock() to a unique value generated
	by incrementing an unsigned 64bit static variable for each assignment
	and then the value of xp_sockref is tested to see if it is equal to
	the value that was saved with the cached reply.

Submitted by:	rmacklem
Reviewed by:	dfr
Approved by:	kib (mentor)

sys/rpc/svc.h

@@ -165,6 +165,7 @@ typedef struct __rpc_svcxprt {
 	int		xp_type;	/* transport type */
 	int		xp_idletimeout; /* idle time before closing */
 	time_t		xp_lastactive;	/* time of last RPC */
+	u_int64_t	xp_sockref;	/* set by nfsv4 to identify socket */
 #else
 	int		xp_fd;
 	u_short		xp_port;	 /* associated port number */