changelog: mention #663 and #664

Signed-off-by: Pires <pjpires@gmail.com>

CHANGELOG.md

@@ -32,6 +32,15 @@
 
   Thanks to [@murphymj25](https://github.com/murphymj25) for the patch.
 
+* [PR #664](https://github.com/fabiolb/fabio/issues/664): Clean-up fabio service entries in Consul on dirty exit
+
+  In the case fabio dies abruptly, the steps to deregister any fabio-related services in Consul will not take place.
+  In certain cases this could result in duplicate service and check entries after fabio restarts, especially if fabio runs in a Docker container.
+
+  This PR addresses this issue by registering an additional TTL check that acts as a deadman switch and removes abandoned service registrations eventually.
+
+  Thanks to [@pires](https://github.com/pires) for the [report](https://github.com/fabiolb/fabio/issues/663) and the fix.
+
 ### [v1.5.11](https://github.com/fabiolb/fabio/releases/tag/v1.5.11) - 25 Feb 2019
 
 #### Breaking Changes