Fix Cycles bug in RR termination, probability should never be > 1.0.

This causes render differences in some scenes, for example fishy_cat
and pabellon scenes render brighter in a few spots. This is an old
bug, not due to recent RR changes.

intern/cycles/kernel/kernel_path_state.h

@@ -187,7 +187,7 @@ ccl_device_inline float path_state_terminate_probability(KernelGlobals *kg, ccl_
 	}
 
 	/* probalistic termination */
-	return average(throughput); /* todo: try using max here */
+	return min(average(throughput), 1.0f); /* todo: try using max here */
 }
 
 /* TODO(DingTo): Find more meaningful name for this */