[2721] Added unit test change comment

ChangeLog

@@ -1,3 +1,7 @@
+5XX.    [func]]       tmark
+	b10-dhcp6: Added unit tests for handling requests when no 
+	v6 subnets are configured/defined. (See Trac #2719)
+	(Trac #2721, git TBD)
 583.	[func]*		jelte
 	b10-cmdctl-usermgr has been updated and its options and arguments
 	have changed; it now defaults to the same accounts file as