set total_instr to 0 before executing plan

kernel/sched/pb.c

@@ -104,6 +104,7 @@ int pb_submit_plan(struct rq *rq)
 	pb->c_entry = 0;
 	pb->count_pb_cycles = 0;
 	pb->count_admin_cycles = 0;
+	pb->total_instr = 0;
 
 	pb->is_initialized = 1;	// must be initialized last