afs: Fix the maximum lifespan of VL and probe calls

If an older AFS server doesn't support an operation, it may accept the call
and then sit on it forever, happily responding to pings that make kafs
think that the call is still alive.

Fix this by setting the maximum lifespan of Volume Location service calls
in particular and probe calls in general so that they don't run on
endlessly if they're not supported.

Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/internal.h

@@ -131,6 +131,7 @@ struct afs_call {
 	int			error;		/* error code */
 	u32			abort_code;	/* Remote abort ID or 0 */
 	u32			epoch;
+	unsigned int		max_lifespan;	/* Maximum lifespan to set if not 0 */
 	unsigned		request_size;	/* size of request data */
 	unsigned		reply_max;	/* maximum size of reply */
 	unsigned		first_offset;	/* offset into mapping[first] */