Update CHANGELOG.md

CHANGELOG.md

@@ -8,6 +8,7 @@ FEATURES:
 IMPROVEMENTS:
 
   * core: Interrupt handling for SIGTERM signal as well. [GH-1858]
+  * builder/amazon-ebs: Add pre-build step, validate unique AMI name [GH-2187]
   * builder/parallels: Support Parallels Desktop 11 [GH-2199]
   * builder/openstack: Add `rackconnect_wait` for Rackspace customers to wait for
       RackConnect data to appear