Add a changes file for 25691/25692

changes/bug25691_again

+  o Minor bugfixes (path selection):
+    - Only select relays when they have the descriptors we prefer to
+      use for them. This change fixes a bug where we could select
+      a relay because it had _some_ descriptor, but reject it later with
+      a nonfatal assertion error because it didn't have the exact one we
+      wanted. Fixes bugs 25691 and 25692; bugfix on 0.3.3.4-alpha.